Hydrogen Passivation and Reactivation of DX Centers in Se-Doped and Si-Doped AIGaAs - -A Comparison
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HYDROGEN PASSIVATION AND REACTIVATION OF DX CENTERS IN Se-DOPED AND Si-DOPED AIGaAs - - A COMPARISON
G. ROOSa),b), N. M. JOHNSONb), C. HERRINGc), AND J. S. HARRIS, Jr.a) a) Department of Electrical Engineering, Solid State Electronics Laboratory, Stanford University, Stanford, CA 94305 b) Xerox Palo Alto Research Center, Palo Alto, CA 94304 0 Department of Applied Physics, Stanford University, Stanford, CA 94305
ABSTRACT The effect of hydrogenation on DX centers was evaluated for both Si- and Se-doped AlxGal-xAs (x=0.26 and 0.23). MBE-grown AIGaAs:Si and MOCVDgrown AIGaAs:Se epilayers were hydrogenated with either monatomic hydrogen or deuterium from a remote plasma at 2500C for lh. The passivation and subsequent reactivation kinetics were studied with C-V and DLTS techniques. Reactivation was investigated in the space-charge layer of Schottky diodes under different bias conditions. While the Group VI and Group IV deep donors respond similarly to passivation, they display significantly different reactivation kinetics, with thermal dissociation energies of 1.5 eV and 1.2 eV for Se-H and Si-H, respectively. These values are close to the energies previously determined for reactivation of the Si and Se shallow donors in both AIGaAs and GaAs. Therefore, they are not significantly dependent on the Al concentration (x - 0.30) even for donors residing on the As sublattice. Our results are consistent with the Chang-Chadi model of DX centers. INTRODUCTION It has been shown that diffusion of monatomic hydrogen can neutralize the electrical activity of shallow donors (1) and acceptors (2) in GaAs and of the Siand Se-related DX centers (DXsi and DXSe) in AIGaAs (3 - 5). The apparent thermal stability of these hydrogen-dopant complexes, compared to similar complexes in silicon, has encouraged consideration of possible technological applications, for example, as a processing step in the fabrication of laser diodes (6, 7) and field effect transistors (8). Furthermore, the passivation of DX centers, obstacles to the performance of various heterojunction devices (9), might improve their performance significantly. For such potential applications, it is necessary to establish a fundamental understanding of the migration and reaction kinetics of hydrogen in GaAs and AIGaAs. Earlier studies have reported values of 2.1 eV (10) and 1.79 eV (11) for the activation energy for the thermal dissociation of the Si-H complex in GaAs. However, it was recently shown that these values represent only an upper limit and that the dissociation energy was closer to 1.2 eV (12,13). Also, Leitch and coworkers (14,15) studied the Mat. Res. Soc. Symp. Proc. Vol. 262. @1992 Materials Research Society
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hydrogen-selenium interaction in GaAs. They determined reactivation energies of 1.52 eV in the electric field of a reverse biased Schottky diode for the Se-H complex and also showed that hydrogen migrates in a negative charge state in Se-doped GaAs. In AIo. 26Gao.74As, values for the dissociation energy of 2.1eV for the DXsi-H complex, and 2.0 eV for th
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