OPTIMIZATION OF UNDOPED GAAS BY LOW-PRESSURE OMVPE USING TRIMETHYLGALLIUM

Optimization of the electrical characteristics of undoped GaAs grown by low-pressure OMVPE using trimethylgallium is presented. The use of a lower growth pressure was found to reduce both the n- and p-type background impurity incorporation. Both electrical and optical measurements revealed that the arsine partial pressure controls the background impurity level during low-pressure growth. Variation of this parameter allowed the attainment of both high mobility (maximum of 136,000 cm2/V-sec at 77 K in this study) and high resistivity layers suitable for field-effect transistor buffers. AlGaAs/GaAs two-dimensional electron gas structures and GaAs MESFETs using the high resistivity buffer layers showed excellent electrical characteristics. Similar trends were obtained using different AsH3 sources despite variations in purity.