High-transconductance p-channel modulation-doped AlGaAs/GaAs heterostructure FET's

p-channel modulation-doped AlGaAs-GaAs heterostructure FET's (p-HFET's) employing two-dimensional hole gas (2DHG) were fabricated under various geometrical device parameter conditions. The p-HFET characteristics were measured at 300 and 77 K for the following three device-parameter ranges: the gate length L
g
(1-320 µm), the gate-source distance L
gs
(0.5-5 µm), and the layer thickness d
t
(35-58 nm) of AlGaAs beneath the gate. Based on the obtained results, a high-performance enhancement-mode p-HFET was fabricated with the following parameters:
L_{g} = 1
µm,
L_{gs} = 0.5
µm, and
d_{t} = 35
nm. The achieved extrinsic transconductance g
m
was 75 mS . mm
^-1
at 77 K. This experimental result indicates that a g
m
greater than 200 mS . mm
^-1
at 77 K Can be obtained in 1-µm gate p-HFET devices.