SOME EFFECTS OF INDIUM COMPOSITION ON PSEUDOMORPHIC INXGA1-XAS IN0.52AL0.48AS MODULATION-DOPED HETEROSTRUCTURES GROWN BY MOLECULAR-BEAM EPITAXY/

Pseudomorphic InxGa1-xAs/In0.52Al0.48 As modulation-doped heterostruct ures were grown by molecular beam epitaxy (MBE) on InP(100) substrates over a range of indium compositions from x = 0.53 to 0.75. Low temper ature photoluminescence (PL) measurements show a prominent reduction i n the InGaAs linewidth due to the quantum-size effect as the indium co mposition is increased from its lattice-match value of 0.53. The lowes t linewidth of 6.8 meV was achieved at an indium composition of 0.65, above which an increase in the linewidth was observed due to the overw helming effects of interfacial strain. The Hall mobilities at 300 and 77 K increase in correspondence to the PL linewidth reduction as the i ndium composition is increased. Although initial signs of mobility sat uration can be seen at an indium composition of 0.65, the peak mobilit y at 77 K of 8.9 x 10(4) cm(2)/V . s was achieved at an indium composi tion of 0.70. There is experimental evidence to indicate that the mobi lity enhancement at increasing indium composition is due to an effect of a reduction in the alloy scattering and in the effective mass of th e carriers. It was found that the insertion of an additional In0.53Ga0 .47As interface-smoothing layer between the strained InGaAs channel an d the In0.52Al0.48As spacer layer did not have a significant effect on the mobility enhancement in the heterostructures.