STUDY OF THERMAL-DESORPTION OF UV OZONE OXIDE ON INP

Commercially available (001) InP substrates have been treated by expos ure to UV/ozone to produce surface oxide layers suitable for thermal d esorption prior to epitaxial growth. Thermally induced changes in comp osition and structure of the oxidized surfaces in vacuum have been stu died using Auger electron spectroscopy (AES), reflection high-energy e lectron diffraction (RHEED), and Rutherford backscattering/channeling (RBSC). It is found that for temperatures above 440-450-degrees-C the oxide becomes unstable. Thermal oxide desorption in vacuum above 460-d egrees-C always results in a P-depleted surface. At 460-degrees-C the oxide can be thermally removed without noticeable P loss; however. the time requried for this process is approximately 2 h. Time-dependent A ES results for oxide desorbing at a fixed temperature can be described by assuming a thinning process with a constant thinning rate for shor t annealing times; however, for longer times the desorption rate incre ases considerably. After complete oxide removal, the resulting clean ( 001) InP sur-face shows a 2 x 1 RHEED pattern, while the corresponding measured In surface peak intensity as measured by RBSC is close to th at obtained for a clean MBE grown surface. Significant structural dete rioration of the surface is detected at high temperatures (almost-equa l-to 495-degrees-C) by RHEED nad RBSC. The average O/In composition ra tio of the oxide layer has been determined by ion scattering methods.