N+-InGaAs/InAlAs recessed gates for InAs/AlSb HFET development

In this work, N⁺-InGaAs/InAlAs recessed gates for InAs/AlSb HFET development are presented. Highly doped N⁺-InGaAs cap layers are used to decrease the parasitic resistances in contact and access regions. As-grown modulation-doped epitaxy materials exhibit a Hall mobility of 14,200 cm²/V s and a sheet density of 6.15 ×10¹² cm⁻², while a mobility of 14,600 cm²/V s and a sheet density of 5.61×10¹² cm⁻² are shown after removal of the N⁺-InGaAs cap. Benefiting the energy band lowering using the highly doped cap layers, a low contact resistance of 0.06 Ω-mm is achieved. DC performances of IDSS=862mA/mm and gm, peak=927mS/mm and RF performances of fT=24GHz and fmax=51GHz are demonstrated in a 2.1μm-gate-length device. An fT-Lg product is as high as 51 GH-μm.