GROWTH-STUDIES OF GAP ON SI BY GAS-SOURCE MOLECULAR-BEAM EPITAXY

We report a growth study of Gap films grown by gas-source molecular be am epitaxy on Si substrates oriented 4 degrees off (100) toward [110]. Reflection high-energy electron diffraction (RHEED), high-resolution X-ray diffraction rocking curve (XRC), and scanning electron microscop y (SEM) were used to characterize material quality. Growth studies wer e carried out in terms of the growth temperature, V/III ratio, and Gap film thickness. Two different growth methods were used: one-step dire ct growth and two-step growth, i.e. a thin GaP layer is grown first at a relatively low temperature as a buffer layer, followed by the main GaP layer grown at the normal growth temperature. The results show tha t with the two-step growth, the material quality of Gap can be greatly improved. Investigation of the effect of using different prelayers (A s-2, P-2, Al, Ga, and Ga + Al) on the quality of GaP films reveals tha t the Ga prelayer gives the best result. By optimizing the growth cond itions, GaP films with very smooth surfaces were obtained.