Inverted GaAs/AlGaAs modulation-doped field-effect transistors with extremely high transconductances

Abstract

Inverted GaAdAsGaAs MODFET's with transconductances as high as 1810 mS/mm at 77 K and 1180 mS/mm at 300 K are fabricated using a self-aligned process. The devices have the gateheterojunction interface spacing of only 100 A , and the observed values of the transconductance are limited primarily by the source series resistance and b i the gate current. The MODFET characteristics are interpreted using the charge control velocity saturation model which takes into account the gate current. The obtained results show a great potential of inverted MODFET's for ultrahigh-speed applications.

High-breakdown-voltage Ga0.51In0.49P/GaAs I-HEMT and I2HEMT with a GaInP passivation layer grown by gas source molecular beam epitaxy

“…While most studies have been concentrated in the normal-structure HEMTs, the inverted structure HEMTs (I-HEMT), in which the small bandgap channel is on top of the large bandgap supplying layer, have also been proposed and investigated theoretically and experimentally by Lee and Shur [4], Morkoc et aL[S] and Cirillo et a1. [6]. There are several advantages of the I-HEMT structure.…”

“…It has been shown that the transconductance of the I-HEMT is nearly independent of the doping level in the high bandgap material, while in the normal HEMT the transconductance decreases with reduced doping [7]. Enhanced electron mobility[S] and extremely high transconductance [6] were also observed, which was attributed to the smaller distance between the 2D electrons and the gate in the I-HEMT compared with that of the normal HEMT. For power applications, high breakdown characteristics are also needed.…”