SCHOTTKY-BARRIER HEIGHT MODIFICATION ON HIGH-PURITY LPE GAAS FOLLOWING A SULFUR-BASED ETCH

Nuclear radiation detectors constructed from GaAs Schottky barrier str uctures require control of barrier height if high resolution is to be reproducibly obtained. We have therefore studied the variation of devi ce barrier height after treatment with common etching solutions. The h eights of Au and Al Schottky barriers on respective samples of n- and p-type liquid-phase epitaxial GaAs were found from reverse bias I-V me asurements subsequent to etching with aqua regia and 3H2SO4:H2O2:H2O ( 3:1:1). An increase in barrier height observed after the 3:1:1 etch wa s found to be a consequence of sulphur contamination. This result is c onsistent with those reported for deliberate sulphur passivation of Ga As. Low diode ideality factors, from 1.007 to 1.064, were measured for layers with carrier concentrations in the range 4 x 10(14) cm-3 to 2. 5 x 10(16) cm-3. A comparison was made between samples etched in the 3 :1:1 solution at 5-degrees-C and at 100-degrees-C. C-V measurements ga ve anomalously large barrier heights for those samples etched at 5-deg rees-C, indicating the formation of a significant interfacial layer pr ior to Schottky barrier metallization, while x-ray photoelectron spect roscopy measurements confirmed the presence of a large oxide layer. No such anomalies were observed for the samples etched in 3:1:1 at 100-d egrees-C.