ELECTRON-TRANSPORT IN GASB INAS HOT-ELECTRON TRANSISTOR GROWN BY METALORGANIC CHEMICAL-VAPOR-DEPOSITION

GaSb/InAs hot electron transistors (HETs) composed of a type-II misali gned quantum well operate at room temperature. The collector current i s well described by the thermionic emission from the emitter. In order to get insight of the electron transport in the HET, the base width w as varied or the collector barrier was modulated. The emitter's barrie r height for the thermionic emission decreases with decreasing base wi dth. This is caused by the increase of the quantum confinement energy in the InAs base with decreasing base width. Among HETs with a GaSb co llector, a GaInSb abrupt layer, or a GaInSb graded layer at the collec tor edge, the latter type has the largest collector current. This indi cates that collector grading reduces not only the collector barrier he ight, but also the quantum mechanical reflection of electrons. Collect or-graded HETs with a 5 nm-thick base show a current gain of 8. The sh eet resistance of InAs base is one order of magnitude less than bulk I nAs without doping. This reduction is partly due to the accumulation o f electrons transferred from the GaSb valence band to the InAs conduct ion band.