An In0.2Ga0.8As/GaAs, modulation-doped, strained-layer superlattice field-effect transistor

For the first time, field-effect transistor action has been demonstrated in InGaAs/GaAs strained-layer superlattice (SLS) material. The samples, prepared by MBE, utilized 17 periods (repeat distance, 300Å) of alternating, modulation-doped, In0.2Ga0.8As and GaAs layers to form the channel of the device. Gate control was realized by use of an Al Schottky diode on the top and a p-n junction diode, formed between the superlattice and a p-type In0.1Ga0.9As buffer layer, on the bottom. At room temperature a representative transistor with a 2.5 µm gate length displayed a characteristic drain saturation current, IDSS, of 64mA ( V, V), a double-gate pinchoff voltage, Vp, of 3.1V( V, % of IDSS) and a maximum, double-gate, normalized, extrinsic transconductance, gmo, of 84mS/mm (VDS=4V). At 77K, IDSSincreased to 98mA, VPremained approximately constant at 3.2V, and gmoincreased to 140mS/mm.