The epitaxial growth of gallium arsenide (GaAs) by organometallic vapor phase epitaxy (OMVPE) has been used to grow various III-V and II-VI compound semiconductors and for electronic and optoelectronic devices. Optimizing the reactor design for OMVPE growth has been done by, for example gas flow visualization and numerical simulation. A major advantage of OMVPE over molecular beam epitaxy (MBE) is that the growth rates of the former can be four to ten times higher than MBE, making feasible the production of electronic devices on a large volume scale. The OMVPE throughput and yield in large- scale device fabrication could be enhanced if complete in-situ device processing, such as etching, patterning and regrowth were demonstrated. The advantage of such processing are: (1) potential for fabrication of low-loss buried waveguides and low threshold buried diode lasers (2) simplified processing (3) low contamination The PIs are therefore working at interfaces developing a simple dry etching process with capabilities for in-situ, large area etching without contaminant introduction or surface degradation. In this study, they plan to investigate the in-situ dry chemical etching of GaAs and AlGaAs using methyl radical sources. The PIs plan to study the "reverse growth" or "etching" of GaAs using several methyl radical-sources at near atmospheric pressure typical in OMVPE growth. These studies will identify the most promising source and operating conditions for the in-situ etching of GaAs in OMPVE reactors without impurity buildup and/or surface morphology changes. Azomethane, iodomethane, hydrogen iodide, and trimethyl arsenic will be examined as source compounds at temperatures in the range of 300-600oC. Another objective is to examine the orientation dependence of etching. Patterned substrate with different crystal orientations exposed will be studied. The anisotrophy of etching will also be examined with masked substrate. Additionally, the work aims at identifying the conditions and understanding the process leading to "poor" etching regimes as evidenced by either substrate morphology changes or the incorporation of impurities.
