ACCURATE CONTROL OF AS AND SB INCORPORATION RATIO DURING SOLID-SOURCE MOLECULAR-BEAM EPITAXY

This paper reports an accurate method for controlling the As/Sb ratio in group-V alloys such as AlAsxSb1-x by modulating As, and Sb, beams during molecular beam epitaxy (MMBE). Experimental results show that the AlAs mole fraction is linearly proportional to the As-shutter duty-cycle, which is easy to control and extremely reproducible. Compared with conventional MBE the MMBE technique dramatically reduces the degree of dependence of AlAs mole fraction on the As-2 flux about an order of magnitude, providing a very straightforward means to obtain group-V alloys with required composition without changing group-V effusion-cell temperatures. X-rap diffraction measurements reveal that the typical lattice mismatch for thick AlAsxSb1-x cladding layers in laser structures grown on InAs is less than 6.5 x 10(-4). In addition, MMBE dramatically improves the surface morphology and crystalline quality. Based on these improvements, room temperature photoluminescence from GaAs0.08Sb0.92/AlAs0.16Sb0.84 single quantum well structures and cw operation of InAs/AlAs0.16Sb0.84 lasers up to 95 K are also observed for the first time. It is expected that this method can also be applied to the MBE growth of other group-V alloys.