Dept of Engineering Physics
Email: Yung Kee Yeo
Ph.D., Physics, University of Southern California, Los Angeles, California, 1972
B.S., Physics, Seoul National University, Seoul, Korea, 1961
Research interests are in the area of experimental semiconductor physics and devices with an emphasis on semiconductor material and device characterization. The electrical, magnetic, and optical properties of elemental, compound, ternary, and quaternary semiconductors are characterized using techniques, such as temperature dependent Hall-effect/sheet resistivity; temperature dependent capacitance-voltage; current-voltage; deep level transient spectroscopy; superconducting quantum interference device; magnetic circular dichroism; cathodo-luminescence; photoluminescence; selective excitation luminescence; time resolved photoluminescence; electroluminescence; and absorption spectroscopy measurements. Current research includes the studies of Wide Bandgap Semiconductors, such as AlxGa1-xN, including GaN, InGaN, and ZnO, which receive extensive attention for their various device applications in the next generation of photonic devices, high temperature electronics, and spin transport electronics (spintronics), bulk ternary III-V Narrow Bandgap Semiconductors, such as InGaAs, InAsP, and InGaSb for long wavelength optoelectronic applications that are beyond the capability of today's epilayer semiconductor devices, and Si- and Ge-based newly developed dircect bandgap Ge1-ySny and Ge1-x-ySixSny alloy semiconductors grown on either Si or Ge substrate for new novel infrared optoelectronic devices. These research programs include studying undoped, doped, and ion-implanted narrow to wide bandgap semiconductors. The doped or implanted ion species include shallow donors and acceptors, transition metals, and rare earths. Through the electrical and optical characterization studies, the exact nature, origins, energy levels, and behavior of the dopant impurities and defects in the materials and their effects on devices are investigated. The magnetic characterization studies of dilute magnetic semiconductors provide useful magnetic properties, such as coercive field and saturation magnetization of the materials and transition temperature for application to the spintronics.
CATHODOLUMINESCENCE
CHARACTERIZATION OF WIDE-BANDGAP OPTICALLY ACTIVATED HIGH-POWER SEMICONDUCTOR DEVICES
DEEP LEVEL TRANSIENT SPECTROSCOPY
EXPERIMENTAL SOLID STATE PHYSICS
MATERIAL CHARACTERIZATION OF NARROW-GAP SEMICONDUCTORS FOR MID-INFRARED OPTO-ELECTRONIC DEVICES
NARROW-BAND GAP MATERIAL STUDIES
PHOTOLUMINESCENCE
SEMICONDUCTOR PHYSICS
SOLID STATE PHYSICS
SUPERCONDUCTING QUANTUM INTERFERENCE DEVICE
113. “Ion-dose and anneal-temperature dependent studies of silicon-implanted AlxGa1-xN,” E.A. Moore, Y.K. Yeo, and Mee-Yi Ryu, Current Applied Physics 2011
112. “Complementary metal-oxide semiconductor-compatible detector materials with enhanced 1550 nm responsivity via Sn-doping of Ge/Si(100),” R. Roucka, R. Beeler, J. Mathews, Mee-Yi Ryu, Y.K. Yeo, J Menendez, and J. Kouvetakis, J. of Applied Physics 109, 103115-1~103115-9 (2011).
111. “Optical and Electrical Properties of Bulk-Grown Ternary InxGa1-xAs,” Y.K. Yeo, A.C. Berstrom, R.L. Hengehold, J.W. Wei, S. Guha, G. Rajagopalan, and Mee-Yi Ryu, J. Korean Phys. Soc. 58, 1267-1273 (2011)
110. “Electrical and Optical Characterization of Melt Grown Bulk InAs1-yPy Crystals,” J. Wei, J. Barnes, S. Guha, L.P. Gonzalez, Y.K. Yeo, R.L. Hengehold, and G. Rajagopalan, J. Electronic Materials 40, 103-108 (2011).
109. “Electrical Activation Studies of Si-Implanted AlxGa1-xN with Aluminum Mole Fraction of 11% to 51%,” E.A. Moore, Y.K. Yeo, Mee-Yi Ryu, and R.L. Hengehold, J. Electronic Materials 40, 11-16 (2011).
108. “Temperature-Dependent Studies of Si-Implanted Al0.33Ga0.67N with Different Annealing Temperature and Times,” E.A. Moore, Y.K. Yeo, G.J. Gruen, Mee-Yi Ryu, and R. L. Hengehold, J. Electronic Materials 39, 21-28 (2010).
107. “Activation Studies of Si-Implanted Al0.45Ga0.55N by Using Cathodoluminescence and Temperature-Dependent Hall-Effect Measurements,” E.A. Moore, Y.K. Yeo, R.L. Hengehold, and Mee-Yi Ryu, J. Korean Phys. Soc. 55, 2465-2469 (2009).
106. "Structural and Optical Characterization of Si-implanted Al0.18Ga0.82N," Mee-Yi Ryu, Y.K. Yeo, and R.L. Hengehold, Solid State Comm. 149, 319-321 (2009).
105. “Nearly Perfect Electrical Activation Efficiencies from Silicon-Implanted AlxGa1-xN with High Aluminum Mole Fraction,” E.A. Moore, Y.K. Yeo, Mee-Yi Ryu, and R.L. Hengehold, J. Electronic Materials 38, 153-158 (2009).
104. “Electroluminescence of n-Zn1-xMgxO/p-Zn1-xMgxO Heterostructures Grown on Si-Substrates,” Sh.U. Yuldashev, P.K. Khabibullaev, R.A. Nusretov, I.V. Khvan, Y.K. Yeo, R.L. Hengehold, and T.W. Kang, J. Korean Phys. Soc. 53, 2913-2916 (2008).
103. “Magnetic Properties of Transition Metal Implanted ZnO Nanotips Grown on Sapphire and Quartz,” J.A. Raley, Y.K. Yeo, R.L. Hengehold, and M.Y. Ryu, J. Magnetics 13, 19-22 (2008).
102. “Ferromagnetic Properties of Nickel Implanted Al0.35Ga0.65N,” J.A. Raley, Y.K. Yeo, R.L. Hengehold, Mee-Yi Ryu, Y. Lu, and Pan Wu, J. Korean Physical Society 51, 1707-1712 (2007).
101. "Magnetic Properties of Fe implanted ZnO nanotips grown by metalorganic chemical vapor deposition," P. Wu, G. Saraf, Y. Lu, D.H. Hill, D.A. Arena, R.A. Bartynski, F. Cosandey, J.F. AlSharab, L. Wielunski, R. Gateau, J. Dvorak, A. Moodenbaugh, J.A. Raley, and Yung Kee Yeo, J. Electronic Materials 36, 529-532 (2007).
100. “Implantation damage recovery and carrier activation studies of Si-implanted Al0.18Ga0.82N by temperature dependent Hall-effect measurements,” Mee-Yi Ryu, Y.K. Yeo, and R.L. Hengehold, Physica Status Solidi (c) 4, 2613-2616 (2007).
99. “Room Temperature Ferromagnetism in Mn Ion Implanted Epitaxial ZnO Films,” D.H. Hill, D.A. Arena, R.A. Bartynski, P. Wu, G. Saraf, Y. Lu, R. Gateau, J. Dvorak, A. Moodenbaugh, and Yung Kee Yeo, Physica Status Solidi (a) 203, 3836-3843 (2006).
98. “Ferromagnetism in Fe-implanted a-plane ZnO Films,” Pan Wu, Gaurav Saraf, Yicheng Lu, David Hill, R. Gateau, Leszek S. Wielunski, Robert A. Bartynski, D.A. Arena, J. Dvorak, A. Moodenbaugh, T. Siegrist, Jeremy A. Raley, and Y.K. Yeo, Appl. Phys. Lett. 89, 012508 (2006).
97. “Electrical and optical activation studies of high dose Si-implanted Al0.18Ga0.82N,” Mee-Yi Ryu, Y.K. Yeo, M.A. Marciniak, and R.L. Hengehold, Solid State Comm. 139, 284-288 (2006).
96. “Room temperature ferromagnetic properties of transition metal implanted Al0.35Ga0.65N,” Jeremy A. Raley, Y.K. Yeo, R.L. Hengehold, M.Y. Ryu, and T.D. Steiner, J. Alloys and Compounds 423, 184-187 (2006).
95. “Electrical characterization of Si-ion implanted AlxGa1-xN annealed at lower temperatures,” Mee-Yi Ryu, Y.K. Yeo, T.W. Zens, M.A. Marciniak, R.L. Hengehold, and T.D. Steiner, Physica Status Solidi (a) 203, 1650-1653 (2006).
94. “Electrical and optical characterization studies of lower dose Si-implanted AlxGa1-xN,” Mee-Yi Ryu, Y.K. Yeo, M.A. Marciniak, T.W. Zens, E.A. Moore, R.L. Hengehold, and T.D. Steiner, J. Electronic Materials 35, 647-653 (2006).
93. “Non-charge related mechanism affecting capacitive MEMS switch lifetime,” Jay F. Kucko, James C. Petrosky, J. Robert Reid, and Yung Kee Yeo, IEEE Microwave and Wireless Components Letters 16, 140-142 (2006).
92. “Electrical and optical activation studies of Si-implanted GaN,” J.A. Fellows, Y.K. Yeo, Mee-Yi Ryu, and R.L. Hengehold. J. Electronic Materials 34, 1157-1164 (2005).
91. “Radiation-induced electron traps in Al0.14Ga0.86N by 1 MeV electron radiation,” Michael R. Hogsed, Y.K. Yeo, Mo Ahoujja, Mee-Yi Ryu, J.C. Petrosky, and R.L. Hengehold, Appl. Phys. Lett. 86, 261906 (2005).
90. “Excitonic transitions in (Ga1-xMnx)N thin films with high Curie temperature,” Hee Chang Jeon, Ji Ah Lee, Yoon Shon, Seung Joo Lee, Tae Won Kang, Tae Whan Kim, Yung Kee Yeo, Yong Hun Cho, and Mun-Deok Kim, J. Crystal Growth 278, 671-674 (2005).
89. “Electrical Characterization of As and [As+Si] doped GaN Grown by Metalorganic Chemical Vapor Deposition,” Mo Ahoujja, Said Elhamri, Rex Berney, Y.K. Yeo, and R.L. Hengehold, Mater. Res. Soc. Symp. Proc. 831, E3.19 (2005).
88. “Electrical and optical properties of 1 MeV-electron irradiated AlxGa1-xN,” Michael R. Hogsed, M. Ahoujja, Mee-Yi Ryu, Y.K. Yeo, J.C. Petrosky, and R.L. Hengehold, Mater. Res. Soc. Symp. Proc. 831, E11.35.1 (2005).
87. “Optical study of implantation damage recovery from Si-implanted GaN,” J.A. Fellows, Y.K. Yeo, Mee-Yi Ryu, and R.L. Hengehold, Solid State Commun. 133, 213-217 (2005).
86. “Electrical activation studies of Si-implanted AlxGa1-xNas a function of ion dose, anneal temperature, and anneal time,” M.Y. Ryu, Y.K. Yeo, E.A. Moore, R.L. Hengehold, and T. Steiner, J. Korean Phys. Soc. 45, S522-S525 (2004).
85. “High electrical activation efficiency obtained from Si-implanted Al0.18Ga0.82N,” Mee-Yi Ryu, Y.K. Yeo, M.A. Marciniak, R.L. Hengehold, and T.D. Steiner, J. Appl. Phys. 96, 6277-6280 (2004).
84. “Ion-beam induced sharpening of ZnO nanotips,” Pan Wu, Gaurav Saraf, Yicheng Lu, David Hill, Leszek S Wielunski, Robert A. Bartynski, Mee-Yi Ryu, Jeremy A. Raley, and Y.K. Yeo, Appl. Phys. Lett. 85, 1247 (2004).
83. “Photoluminescence characterization of defects introduced in 4H-SiC during high energy proton irradiation and their annealing behavior,” Mo Ahoujja, H.C. Crocket, M.B. Scott, Y.K. Yeo, and R.L. Hengehold, Mat. Res. Soc. Symp. Proc. 815, J5.21 (2004).
82. “Electrical and optical activation studies of Si-implanted AlxGa1-xN by Hall-effect and photoluminescence measurements,” M.Y. Ryu, Y.K. Yeo, E.A. Chitwood, R.L. Hengehold, and T. Steiner, 2003 International Symposium on Compound Semiconductors, San Diego, California, 2003, IEEE 22-27 (2004).
81. “Annealing Studies of Si-Implanted Al0.25Ga0.75N,” Mee-Yi Ryu, E.A. Chitwood, E.N. Claunch, Y.K. Yeo, R.L. Hengehold, J.A. Fellows, and T.D. Steiner, Physica Status Solidi (c) No. 7, 2593-2596 (2003).
80. “Electrical Characterization of Defects Introduced in 4H-SiC during High Energy Proton Irradiation and Their Annealing Behavior,” M. Ahoujja, H.C. Crocket, M.B. Scott, Y.K. Yeo, and R.L. Hengehold, Mat. Res. Soc. Symp. Proc. 764, C3, 37 (2003).
79. “Annealing Studies of Si-Implanted GaN by Hall-Effect and Photoluminescence Measurements,” J.A. Fellows, Y.K. Yeo, M.Y. Ryu, R.L. Hengehold, and Todd Steiner, Compound Semiconductors 2002, Lausanne, Switzerland, 2002, Inst. Phys. Conf. Ser. No. 174 (Institute of Physics, Bristol and Philadelphia, 2003), pp. 49-52.
78. “Electrical Activation Studies of GaN Implanted with Si from Low to High Dose,” J.A. Fellows, Y.K. Yeo, R.L. Hengehold, and D. Johnstone, Appl. Phys. Lett. 80, 1930-1932 (2002).
77. “Electrical and Optical Studies of Si-Implanted GaN,” J.A. Fellows, Y.K. Yeo, R.L. Hengehold, and L. Krasnobaev, Mat. Res. Soc. Symp. Proc. 693, I6.38.1-6 (2002).
76. “Deep Centers and Their Capture barriers in MOCVD-Grown GaN,” D. Johnstone, M. Ahoujja, Y.K. Yeo, R.L. Hengehold, and L. Guido, Mat. Res. Soc. Symp. Proc. 692, H2.7.1-11 (2002).
75. “Electrical and Optical Investigation of MBE Grown Si-doped AlxGa1-xN as a Function of Al Mole Fraction up to 0.5,” M. Ahoujja, J.L. McFall, Y.K. Yeo, R.L. Hengehold, and J.E. Van Nostrand, Mat. Sci. Eng. B91-92, 285-289 (2002).
74. “Temperature-dependent Hall Measurements of MBE grown Si-doped AlxGa1-xN for Al Mole Fraction up to 0.5,” M. Ahoujja, Y.K. Yeo, R.L. Hengehold, and J.E. Van Nostrand, Appl. Phys. Lett. 80, 1382-1384 (2002).
73. “Optical Characterization of Mg- and Si-Implanted GaN,” J.A. Fellows, Y.K. Yeo, R.L. Hengehold, and L. Krasnobaev, Mat. Res. Soc. Symp. Proc. 680E, E7.1.1-E7.1.6 (2001).
72. "Electrical Properties of MBE grown Si-doped AlxGa1-xN as a Function of Nominal Al Mole Fraction up to 0.5,” M. Ahoujja, Y.K. Yeo, R.L. Hengehold, and J.E. Van Nostrand, Mat. Res. Soc. Symp. Proc. 680E, E3.5.1-E3.5.6 (2001).
71. “Optical Investigation of MBE Grown Si-Doped AlxGa1-xN as a Function of Nominal Al Mole Fraction up to 0.5,” J.L. McFall, R.L. Hengehold, Y.K. Yeo, and J.E. Van Nostrand, J. Crystal Growth 227-228, 458-465 (2001).
70. “Influence of arsenic doping on the electrical properties of GaN epitaxial layers grown by MOCVD,” M. Ahoujja, Y.K. Yeo, R.L. Hengehold, L.J. Guido, P. Mitev, D.K. Johnstone, and Y.K. Kim, Proceedings of the 2000 International Semiconducting and Insulating Materials Conference (SIMC-XI), pp. 27-30, edited by C. Jagadish and N.J. Welham.
69. “Electrical properties of boron doped p-SiGeC grown on n--Si substrate,” M. Ahoujja, Y.K. Yeo, R.L. Hengehold, G.S. Pomrenke, D.C. Look, and Jim Huffman, Appl. Phys. Lett. 77, 1327-1329 (2000).
68. “Hall coefficient singularity observed from p-SiGeC grown on n-Si substrate,” M. Ahoujja, Y.K. Yeo, M.R. Smith, R.L. Hengehold, G.S. Pomrenke, and Jim Huffman, Compound Semiconductors 1999, Berlin, Germany, 1999, Inst. Phys. Conf. Ser. No. 166 (Institute of Physics, Bristol and Philadelphia, 2000), p. 161.
67. “Control of Surface States in GaSb/AlxGa1-xAsySb1-y/GaxIn1-xSb/AlxGa1-xAsySb1-y Quantum Well Structures,” D.K. Johnstone, Y.K. Yeo, R.L. Hengehold, and G.W. Turner, Appl. Phys. Lett. 75, 2779-2781 (1999).
66. “High Temperature (500 oC) Implantation Study of P+ and N+ Implanted Epitaxial N-Type 4H-SiC,” M.B. Scott, Y.K. Yeo, R.L. Hengehold, and J.D. Scofield, Compound Semiconductors 1998, Nara, Japan, 1998, Inst. Phys.Conf. Ser. No. 162 (Institute of Physics, Bristol and Philadelphia, 1999), pp. 763-768.
65. “Recombination Dynamics in InAsSb Quantum-Well Diode Lasers Measured Using Photoluminescence Upconversion,” W.T. Cooley, R.L. Hengehold, Y.K. Yeo, G.W. Turner, and J.P. Loehr, Appl. Phys. Lett. 73, 2890-2892 (1998).
64. “Optical Characterization of MBE-Grown InAs1-xSbx Nearly Lattice Matched to GaSb,” M.A. Marciniak, R.L. Hengehold, Y.K. Yeo, and G.W. Turner, J. Appl. Phys. 84, 480-488 (1998).
63. “Deep Level Defect Study of Ion Implanted (Ar, Mg, Cr) n-Type 6H-SiC by Deep Level Transient Spectroscopy,” M.B. Scott, J.D. Scofield, Y.K. Yeo, and R.L. Hengehold, Mater. Sci. Forum 264-268, 549-552 (1998).
62. “Luminescence and Annealing Studies of Er-Implanted GaN with and without Oxygen Co-doping,” E. Silkowski, Y.K. Yeo, R.L. Hengehold, and L.R. Everitt, Mater. Sci. Forum 258-263, 1577-1582 (1997).
61. “Deep Level Capture Barrier in Molecular Beam Epitaxial Grown AlAsySb1-y Measured by Isothermal Capacitance Transient Spectroscopy,” D.K. Johnstone, Y.K. Yeo, R.L. Hengehold, and G.W. Turner, Appl. Phys. Lett. 71, 506-508 (1997).
60. "Junction Characteristics of Electron-Irradiated Ga0.5In0.5P n+p Diodes and Solar Cells," K.C. Reinhardt, Y.K. Yeo, P.H. Ostdiek, and R.L. Hengehold, J. Appl. Phys. 81, 3700-3706 (1997).
59. "Photoluminescence Study of p-type CdGeAs2 Ordered Semiconductor Crystals," J.E. McCrae, R.L. Hengehold, Y.K. Yeo, M.C. Ohmer, and P.G. Schunemann, Appl. Phys. Lett. 70, 455 (1997).
58. “Photoluminescence Studies of Epitaxial InAsSb and InAsSb:Be Grown on GaSb Substrates,” M.A. Marciniak, R.L. Hengehold, Y.K. Yeo, G.W. Turner, and M.W. Prairie. Compound Semiconductors 1996, St. Petersburg, Russia, 1996, Inst. Phys. Conf. Ser. No. 155 (Institute of Physics, Bristol and Philadelphia, 1997), pp. 865-868
57. “Comparative Study of the Junction Characteristics and Performance of SiC p+/n and Schottky Power Rectifiers,” J.D. Scofield, M.E. Dunn, J.C. Wiemeri, K.C. Reinhardt, Y.K. Yeo, and R.L. Hengehold, Compound Semiconductors 1996, St. Petersburg, Russia, 1996, Inst. Phys. Conf. Ser. No. 155 (Institute of Physics, Bristol and Philadelphia, 1997), pp. 597-600.
56. "Optical Activation of Ion Implanted and Annealed GaN," E. Silkowski, G.S. Pomrenke, Y.K. Yeo, and R.L. Hengehold, Physica Scripta T69, 276-280 (1997).
55. "Defect Dominant Junction Characteristics of 4H-SiC p+-n Diodes,” J.D. Scofield, M.E. Dunn, K.C. Reinhardt, Y.K. Yeo, and R.L. Hengehold, Mat. Res. Soc. Symp. Proc. 423, 57-62 (1996).
54. "Neodymium and Erbium Implanted GaN,” E. Silkowski, Y.K. Yeo, R.L. Hengehold, B.L. Goldenberg, and G.S. Pomrenke, Mat. Res. Soc. Symp. Proc. 422, 69-74 (1996).
53. “Hole Mobility in Doped and Ion Implanted GaAs,” Y.K. Yeo, Properties of Gallium Arsenide, 3rd edition, EMIS Datareviews Series No. 16, edited by M.R. Brozel and G.E. Stillman (INSPEC, IEE, 1996), pp. 91-97.
52. "Annealing Study of Ion Implanted MOCVD and MBE Grown GaN," E. Silkowski, Y.K. Yeo, R.L. Hengehold, M.A. Khan, T. Lei, K. Evans, and C. Cerney, Mat. Res. Soc. Symp. Proc. 395, 813-818 (1996).
51. “Deep Level Investigation of Bulk and Epitaxial 6H-SiC at High Temperatures,” J.D. Scofield, Y.K. Yeo, and R.L. Hengehold, Compound Semiconductors 1995, Cheju Island, Korea, 1995, Inst. Phys. Conf. Ser. No. 145 (Institute of Physics, Bristol and Philadelphia, 1996), pp. 511-516.
50. “Electrical and Optical Characterization of GaSb Based Diode Laser Material for 2-4 ¿m Applications,” D.K. Johnstone, M.A. Marciniak, Y.K. Yeo, R.L. Hengehold, and G.W. Turner, Compound Semiconductors 1995, Cheju Island, Korea, 1995, Inst. Phys. Conf. Ser. No. 145 (Institute of Physics, Bristol and Philadelphia, 1996), pp. 369-374.
49. “Deep Level Study of As-Grown and Ion Implanted Bulk and MOCVD Grown Epitaxial 6H-SiC,” J.D. Scofield, Y.K. Yeo, and R.L. Hengehold, Silicon Carbide and Related Materials 1995, Kyoto, Japan, 1995, Inst. Phys. Conf. Ser. No. 142 (Institute of Physics, Bristol and Philadelphia, 1996), pp. 329-332.
48. “The Growth and Characterization of Si1-xGex Multiple Quantum Wells on Si(110) and Si(111),” P.E. Thompson, T.L. Kreifels, M. Gregg, R.L. Hengehold, Y.K. Yeo, D.S. Simons, M.E. Twigg, M. Fatemi, and K. Hobart, J. Crystal Growth 157, 21 (1995).
47. “Pr3+ Luminescence in GaAs and AlxGa1-x As Implanted with Pr," P.L. Thee, Y.K. Yeo, R.L. Hengehold, and G.S. Pomrenke, J. Appl. Phys. 78, 4651 (1995).
46. “Si1-xGex/Si Multiple Quantum Wells on Si (100) and Si (110) for Infrared Absorption,” T.L. Kreifels, R.L. Hengehold, Y.K. Yeo, P.E. Thompson, and D.S. Simons, J. Vac. Sci. Technol. A 13, 636 (1995).
45. "Junction Characteristics of Ga0.5In0.5P n+p Diodes and Solar Cells," K.C. Reinhardt, Y.K. Yeo, and R.L. Hengehold, J. Appl. Phys. 77, 5763 (1995).
44. "Er-related Deep Centers in GaAs Doped with Er by Ion Implantation and Molecular Beam Epitaxy," D.W. Elsaesser, Y.K. Yeo, R.L. Hengehold, K.R. Evans, and F.L. Pedrotti, J. Appl. Phys. 77, 3919 (1995).
43. “Hall-effect and Low Temperature Photoluminescence Measurements of Rare-Earth Erbium Implanted GaAs,” Y.Y. Kim and Y.K. Yeo, J. Korean Phys. Soc. 27, 163-167 (1994).
42. "Excitation of the 4f-electron of Pr3+ in GaAs:Pr and AlxGa1-xAs:Pr," P.L. Thee, Y.K. Yeo, R.L. Hengehold, and G.S. Pomrenke, Physica Scripta T54, 24 (1994).
41. "Er-4f Luminescence Excitation and Quenching Mechanisms in GaAs," D.W. Elsaesser, J.E. Colon, Y.K. Yeo, R.L. Hengehold, and G.S. Pomrenke, Mater. Sci. Forum. 143-147, 749 (1994).
40. "Polarized Luminescence Study of Ordered Nonlinear Optical Material ZnGeP2," J.E. McCrae, Jr., M.R. Gregg, R.L. Hengehold, Y.K. Yeo, P.H. Ostdiek, M.C. Ohmer, P.G. Schunemann, and T.M. Pollak, Appl. Phys. Lett. 64, 3142 (1994).
39. "Annealing Studies of Er-Implanted GaAs and the Excitation Mechanism of Er in GaAs," D.W. Elsaesser, J.E. Colon, Y.K. Yeo, R.L. Hengehold, and G.S. Pomrenke, Mat. Res. Soc. Symp. Proc. 301, 251 (1993).
38. "Luminescence Study of the Intra-4f Emissions from GaAs:(Er+O) and AlxGa1-xAs:(Er+O)," J.E. Colon, D.W. Elsaesser, Y.K. Yeo, R.L. Hengehold, and G.S. Pomrenke, Mat. Res. Soc. Symp. Proc. 301, 169 (1993).
37. "Enhancement of the Er3+ Emissions from AlGaAs:Er Co-doped with Oxygen," J.E. Colon, D.W. Elsaesser, Y.K. Yeo, R.L. Hengehold, and G.S. Pomrenke, Appl. Phys. Lett. 63, 216 (1993).
36. "Erbium Complexes and Defect Levels in MBE-Grown Erbium-Doped GaAs and AlGaAs," D.W. Elsaesser, J.E. Colon, Y.K. Yeo, R.L. Hengehold, K.R. Evans, and J.S. Solomon, J. Crystal Growth 127, 707 (1993).
35. "A Study of Broad Band Photoluminescence from Si1-xGex/Si Superlattices," T.D. Steiner, R.L. Hengehold, Y.K. Yeo, D.J. Godbey, P.E. Thompson, and G.S. Pomrenke, J. Crystal Growth 127, 472 (1993).
34. "Near Band-Edge Photoluminescence from Si1-xGex/Si Superlattices Grown by Molecular Beam Epitaxy," T.D. Steiner, R.L. Hengehold, Y.K. Yeo, D.J. Godbey, P.E. Thompson, and G.S. Pomrenke, J. Vac. Sci. Technol. B 10, 924 (1992).
33. "Molecular Beam Epitaxial Growth and Characterization of Erbium-Doped GaAs and AlGaAs," K.R. Evans, E.N. Taylor, C.E. Stutz, D.W. Elsaesser, J.E. Colon, Y.K. Yeo, R.L. Hengehold, and J.S. Solomon, J. Vac. Sci. Technol. B 10, 870 (1992).
32. "Excitation Mechanism of the Erbium 4f Emissions in GaAs," J.E. Colon, D.W. Elsaesser, Y.K. Yeo, R.L. Hengehold, and G.S. Pomrenke, Mater. Sci. Forum 83-87, 671 (1992).
31. "Luminescence of Thulium in III-V Semiconductors and Silicon," G.S. Pomrenke, E. Silkowski, J.E. Colon, D.J. Topp, Y.K. Yeo, and R.L. Hengehold, J. Appl. Phys. 71, 1919 (1992).
30. "Study of the Broad Luminescence Bands in Ge-Implanted GaAs Centered at 1.44-1.46 eV," K.J. Keefer, Y.K. Yeo, and R.L. Hengehold, J. Appl. Phys. 70, 4634 (1991).
29. "Near IR Emissions from Er, Tm, and Pr Implanted GaAs and AlGaAs," G.S. Pomrenke, Y.K. Yeo, and R.L. Hengehold, Mat. Res. Soc. Symp. Proc. 216, 415 (1991).
28. "Lantanide (Yb, Er, Tm, Pr, Ho) and Actinide (U) Activated Luminescence in III-V Semiconductors," G.S. Pomrenke, R.L. Hengehold, and Y.K. Yeo, Eur. J. Solid State Inorg. Chem. 28, 159 (1991).
27. "Actinide Activated Luminescence in Uranium Implanted III-V Semiconductors," G.S. Pomrenke, R.L. Hengehold, Y.K. Yeo, I.G. Brown, and J.S. Solomon, J. Appl. Phys. 67, 2040 (1990).
26. "SIMS and Photoluminescence Studies of Rare-Earth Implants in InP," J.S. Solomon, G.S. Pomrenke, R.L. Hengehold, and Y.K. Yeo, Proc. Seventh Internat. Conf. on Secondary Ion Mass Spectrometry, SIMS VII, pp 571-574 (1990).
25. "Excitation Mechanism of Rare-Earth Emissions (Yb, Tm, Er, Pr) in GaAs and InP," G.S. Pomrenke, R.L. Hengehold, and Y.K. Yeo, Gallium Arsenide and Related Compounds 1989, Karuizawa, Japan, 1989, Inst. Phys. Conf. Ser. No. 106 (Institute of Physics, Bristol and New York, 1990), p. 339.
24. "Evaluation of Carrier Distributions in a Depletion Region of Semiconductor Measured by Capacitance-Voltage Profile Method," Y.K. Yeo, G.H. Gainer, Jr., J.H. Kim, and R.L. Hengehold, Appl. Phys. Lett. 56, 75 (1990).
23. "Characterization of Residual Acceptors in SI- and VPE-GaAs by Selective Pair Luminescence and Photoluminescence Methods," J.R. Cavins, Y.K. Yeo, and R.L. Hengehold, J. Electrochem. Soc. 136, 2113 (1989).
22. "Excited States of the Mg Acceptor in GaAs," J.R. Cavins, Y.K. Yeo, and R.L. Hengehold, J. Appl. Phys. 64, 6761 (1988).
21. "Surface Depletion Effect Correction to Non-Uniform Carrier Distributions by Hall Measurements," Y.K. Yeo, R. L. Hengehold, and D.W. Elsaesser, J. Appl. Phys. 61, 5070 (1987).
20. "Substrate Dependent Electrical Properties of Low-Dose Si Implants in GaAs," Y.K. Yeo, R.L. Hengehold, Y.Y. Kim, A. Ezis, Y.S. Park, and J.E. Ehret, J. Appl. Phys. 58, 4083 (1985).
19. "IR Radiation Transient Annealing of Silicon Implanted SI Gallium Arsenide," A. Ezis, Y.K. Yeo, and Y.S. Park, Mat. Res. Soc. Symp. Proc. on Energy Beam Solid Interactions and Transient Thermal Processing, edited by J.C.C. Fan and N.M. Johnson (North Holland, Amsterdam, Netherlands; held in Boston, Massachusetts), 23, 681 (1984).
18. "Rapid Thermal Annealing Characteristics of As- and BF2-Implanted Si," R. Kwor, D.L. Kwong, and Y.K. Yeo, Appl. Phys. Lett. 45, 77 (1984).
17. "Si Implantation in GaAs," R.S. Bhattacharya, A.K. Rai, Y.K. Yeo, P.P. Pronko, S.C. Ling, S.R. Wilson, and Y.S. Park, J. Appl. Phys. 54, 2329 (1983).
16. "Sulphur Implantation in GaAs," R.S. Bhattacharya, A.K. Rai, Y.K. Yeo, P.P. Pronko, and Y.S. Park, Nuclear Instruments and Methods, 209/210, Part II, 637 (1983).
15. "A Detailed SI GaAs Substrate Study: Conversion and MESFET Properties," D.C. Look, P.W. Yu, J.E. Ehret, Y.K. Yeo, and R. Kwor, Semi Insulating III V Materials, edited by S. Makram Ebeid and B. Tuck (Shiva, England; held in Evian, France), 372 (1982).
14. "Correlation of Electrical Carrier and Atomic Profiles of Mg Implants in GaAs," Y.K. Yeo, Y.S. Park, F.L. Pedrotti, and B.D. Choe, J. Appl. Phys. 53, 6148 (1982).
13. "Fluence Dependence of Displacement Damage, Residual Defects, and Electrical Properties of High Temperature Annealed Se+-Implanted GaAs," R.S. Bhattacharya, P.P. Pronko, Y.K. Yeo, A.K. Rai, Y.S. Park, and J. Narayan, J. Appl. Phys. 53, 4821 (1982).
12. "Electrical Properties and Distribution of S Implants in GaAs," R. Kwor, Y.K. Yeo, and Y.S. Park, J. Appl. Phys. 53, 4786 (1982).
11. "Correlation of Electrical Carrier and Atomic Profiles of S Implants in GaAs," Y.K. Yeo, Y.S. Park, and R. Kwor, J. Appl. Phys. 53, 1815 (1982).
10. "Ion Energy Dependent Electrical Properties of Sulfur Implants in GaAs," Y.K. Yeo, R. Kwor, and Y.S. Park, J. Appl. Phys. 53, 1812 (1982).
9. "Dual Implantation and Amphoteric Behavior of Ge Implants in GaAs," Y.S. Park, Y.K. Yeo, and F.L. Pedrotti, Nuclear Instruments and Methods, 182/183, Part II, 617 (1981).
8. "Comparative Studies of Mg Implants in GaAs in Different Annealing Environments," Y.K. Yeo, Y.S. Park, and B.D. Choe, Nuclear Instruments and Methods, 182/183, Part II, 609 (1981).
7. "Modification of the Amphoteric Activity of Ge-Implants in GaAs by Dual Implantation of Ge and As," Y.K. Yeo, F.L. Pedrotti, and Y.S. Park, J. Appl. Phys. 51, 5785 (1980).
6. "Dual Implantation of Ga and Ge into GaAs," F.L. Pedrotti, Y.K. Yeo, J.E. Ehret, and Y.S. Park, J. Appl. Phys. 51, 5781 (1980).
5. "Distribution of Electrically Active Mg Implants in GaAs," B.D. Choe, Y.K. Yeo, and Y.S. Park, J. Appl. Phys. 51, 4742 (1980).
4. "Laser Annealing of Ion Implanted GaAs," Q. Kim, Y.S. Park, R.S. Mason, T.E. Luke, R.L. Hengehold, and Y.K. Yeo, AIP Conf. Proc. on Laser Solid Interactions and Laser Processing 1978, edited by S.D. Ferris, H.J. Leamy, and J.M. Poate (American Institute of Physics, New York; held in Boston, Massachusetts) No. 50, 597 (1979).
3. "Electrical Measurements and Optical Activation Studies in Mg-Implanted GaAs," Y.K. Yeo, Y.S. Park, and P.W. Yu, J. Appl. Phys. 50, 3274 (1979).
2. "Amphoteric Behavior of Ge Implants in GaAs," Y.K. Yeo, J.E. Ehret, F.L. Pedrotti, Y.S. Park, and W.M. Theis, Appl. Phys. Lett. 35, 197 (1979).
1. "A Superconducting Second Derivative Gradiometer, J.E. Opfer, Y.K. Yeo, J.M. Pierce, and L.H. Rorden, IEEE Trans. Magn, Mag 10, 536 (1974).