IR Radiation Transient Annealing of Silicon Implanted SI Gallium Arsenide
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IR RADIATION TRANSIENT ANNEALING OF SILICON IMPLANTED SI GALLIUM ARSENIDE
A. EZIS*,Y. K. YEO,* Y. S. PARK,," *Universal Energy Systems, Inc., 4401 Dayton-Xenia Road, Dayton, Ohio 45432; **AFWAL/AADR, Wright-Patterson Air Force Base, Ohio 45433.
ABSTRACT The electrical properties of IR radiation transient annealed Si implanted semi-insulating GaAs are presented for 100 keV ion doses from 3 x 1012 to 3 x 1014 cm-2. 2 For wafers implanted with 3 x 1012 cmdoses, suitable for FET channel layers, carrier concentration and drift mobility profiles were determined from C-V and transconductance measurements on fat FET structures. Optimum electrical activation and carrier concentration profiles were obtained for peak pulse temperatures of 930-950*C. Van der Pauw measurements were made on 2 substrates implanted with Si doses > 1 x 1013 cmto determine sheet carrier concentration and Hall mobility. The peak pulse temperature required to give optimum activation efficiency is found to increase with dose. The results presented here demonstrate that undoped substrates are preferable to Cr-doped substrates for low dose device applications.
INTRODUCTION Ion implantation of SI GaAs has been established as an important technique for producing both active and contact layers suitable for device applications. Activation of implanted donor atoms, e.g., Si requires high temperature annealing and this has been carried out conventionally by furnace annealing at temperatures of 800-850'C for 10-30 minutes. However, the choice of substrate is a critical factor in determining the electrical characteristics of the subsequently implanted and annealed layer. Minimization of the diffusion of implanted donor species during annealing is essential for producing abrupt doping profiles and good uniformity over the implanted layer. This condition generally restricts the choice of substrate to ones which retain their semi-insulating character at high temperatures and do not undergo type conversion which may distort the carrier concentration profile. Transient annealing has been recently applied to Si implanted SI GaAs substrates in an attempt to reduce diffusion effects and improve electrical activation efficiencies [1]-[5]. Here, the most widely used method of annealing has employed an arrangement of halogen lamps to irradiate uniformly the implanted sample at temperatures > 900'C for a few seconds. Annealing has been carried out both with and without encapsulation. However, for the latter case, it has been found that, with the implanted surface placed face down on either a silicon or GaAs wafer, the anneal cycle had to be restricted to certain temperatures and times
[1]. In this paper results on transient annealing of both Si implanted undoped and Cr-doped substrates are presented for doses suitable for FET active and contact layers. Carrier concentration and drift mobility profiles are evaluated for transient and furnace annealed low dose Si implanted substrates in order to draw a comparison between the two techniques. Mat. Res. Soc.Symp. Proc. Vol.
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