High-Temperature Illumination-Induced Metastability in Undoped Semi-Insulating GaN Grown by Metalorganic Vapor Phase Epi
- PDF / 156,541 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 92 Downloads / 187 Views
L11.33.1
High-Temperature Illumination-Induced Metastability in Undoped Semi-Insulating GaN Grown by Metalorganic Vapor Phase Epitaxy Z-Q. Fang1, B.B. Claflin1, D.C. Look1, T.H. Myers2, D.D. Koleske3a, A.E. Wickenden3b, and R.L. Henry3 1 Semiconductor Research Center, Wright State University, Dayton, OH 45435 2 Physics Department, West Virginia University, Morgantown, WV 26506 3 Electronics Science and Technology Division, Naval Research Laboratory, Washington, DC 20375 a Sandia National Laboratories, Albuquerque, NM 87185 b Army Research Laboratory, AMSRL-SE-RL, Adelphi, MD 20783 ABSTRACT High-temperature (high-T) illumination-induced metastability in undoped semi-insulating (SI) GaN grown on a-plane sapphire by metalorganic vapor phase epitaxy has been studied using thermally stimulated current (TSC) spectroscopy, photocurrent (PC) and persistent photocurrent (PPC) measurements. The metastability can be induced by illumination at 390>T>300K (using either white or 360-nm light), followed by cooling the sample to 83 K in the dark. Without highT illumination, the SI-GaN sample stays in its normal state (“off” state), and shows at least six TSC traps, B (0.63 eV), Bx (0.51 eV), C1 (0.44 eV), C (0.32 eV), D (0.23 eV), and E (0.16 eV). However, after high-T illumination the sample goes into a metastable state (“on” state), and shows a strong increase in both the PC at 83 K and the TSC of traps D, C, and E, accompanied by significant change in their relative densities. PPC at 83 K in the “on” state lasts much longer than that in the “off” state. Association of possible point defects and dislocations with the metastability behavior will be discussed. INTRODUCTION Undoped semi-insulating (SI) GaN films are preferred for device structures such as AlGaN/GaN HEMTs. Recently, yellow-luminescence (YL) related optical metastability or memory effects in undoped GaN layers have been studied using photoluminescence (PL) or cathodoluminescence (CL), in conjunction with exposures of samples to either high-intensity ultraviolet light or electron-beam irradiation at room temperature [1,2]. Instead of PL or CL, we have successfully used thermally stimulated current (TSC) spectroscopy, both illuminationtemperature and time dependent, and photocurrent (PC), to study photo-induced metastability in undoped SI-GaN samples grown by metalorganic vapor phase epitaxy. The metastability is induced by high-temperature (high-T) illumination at 390>T>300 K (using white or 360-nm light), followed by cooling the sample to 83 K in the dark. Without high-T illumination, the SIGaN sample stays in its normal state (or “off” state) and shows at least six TSC traps, B (0.63 eV), Bx (0.51 eV), C1 (0.44 eV), C (0.32 eV), D (0.23 eV), and E (0.16 eV). These traps are very similar to the electron traps observed in n-type GaN films by deep level transient spectroscopy (DLTS). High-T illumination puts the sample into a metastable state (or “on” state), which shows a strong increase in both the PC at 83 K and the TSC of traps D, C, and E. The TSC traps also show
Data Loading...
