HIGHLY STRAINED IN0.5GA0.5P AS WIDE-GAP MATERIAL ON INP SUBSTRATE FORHETEROJUNCTION FIELD-EFFECT TRANSISTOR APPLICATION

Ga0.5In0.5P has been evaluated as a highly strained Al-free wide gap m aterial for heterostructure field-effect transistor (HFET) application on InP substrates using the metalorganic vapour phase epitaxy (MOVPE) technique. The growth mode has been studied including the separate an alysis of group-V and group-III exchange by means of photoluminescence (PL), X-ray, and scanning transmission electron microscopy (STEM) mea surements, respectively. X-ray and STEM measurements indicate that the lower interface is abrupt within the resolution of our methods while the upper interface shows group-III intermixing with a length dependin g on the thickness of the strained In0.5Ga0.5P. In agreement with the abrupt lower interface Hall measurements show no impact of a 2.5 nm In 0.5Ga0.5P spacer layer directly at the channel interface on transport properties (mu(H,300K) > 11,000 cm(2)/V.s). The Ga0.5In0.5P spacer lay er provides an increased valence band discontinuity which acts as a ho le barrier. The negative influence of holes generated in the small ban d gap InGaAs channel material at high drain bias is suppressed and imp roved DC and RF data are achieved. For examples, at V-DS = 5.5 V, a cu t-off frequency of f(max) > 150 GHz is obtained for a 0.7 mu m gate le ngth device.