Use Of Annealed Low-Temperature Grown Gaas As A Selective Photoetch-Stop Layer

We demonstrate annealed low-temperature grown (LTG) GaAs to be a highly effective etch-stop layer while photoetching n-type normal-growth-temperature GaAs. During this process, the etch rate is controlled by the transport of photogenerated carriers to the semiconductor/electrolyte interface. Because of the very short minority carrier lifetime in LTG-GaAs, only a very small portion of photogenerated carriers can reach the semiconductor surface to complete the electrolytic decomposition reaction. Therefore, the etch rate of LTG-GaAs is reduced considerably. In our studies, the etch rate selectivity can be as high as 800. Furthermore, we demonstrate that doping concentration, presence of an ohmic contact, photon energy, and pH value of the etching solution can be used to control the etch rate of n-GaAs during the photoetching process. (C) 1996 American Institute of Physics.