InAlAs/InGaAs Pseudomorphic High Eelectron Mobility Transistors Grown by Molecular Beam Epitaxy on the InP Substrate

A novel PMMA/PMGI/ZEP520 trilayer resist electron beam lithograph (EBL) technology is successfully developed and used to fabricate the 150 nm gate-length In_0.7Ga_0.3As/In_0.52Al_0.48As Pseudomorphic HEMT on an InP substrate, of which the material structure is successfully designed and optimized. A perfect profile of T−gate is successfully obtained. These fabricated devices demonstrate excellent dc and rf characteristics: the transconductance G_m, maximum saturation drain−to-source current I_DSS, threshold voltage V_T, maximum current gain frequency f_T derived from h₂₁, maximum frequency of oscillation derived from maximum available power gain/maximum stable gain and from unilateral power−gain of metamorphic InGaAs/InAlAs high electron mobility transistors (HEMTs) are 470 mS/mm, 560 mA/mm, -1.0 V, 76 GHz, 135 GHz and 436 GHz, respectively. The excellent high frequency performances promise the possibility of metamorphic HEMTs for millimeter-wave applications.