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 cm
²
/V s and a sheet density of 6.15 ×10
¹²
cm
^-2
, while a mobility of 14,600 cm
²
/V s and a sheet density of 5.61 × 10
¹²
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 I
_DSS
= 862 mA/mm and g
_{m, peak}
= 927 mS/mm and RF performances of f
_T
= 24 GHz and f
_max
= 51 GHz are demonstrated in a 2.1μm-gate-length device. An f
_T
-L
_g
product is as high as 51 GH-μm.