Performance of Al_0.24Ga_0.76As/In_0.22Ga_0.78As double-heterojunction HEMTs with an as deposited and a buried gate

Abstract

Depletion-mode Al 0.24 Ga 0.76 As/In 0.22 Ga 0.78 As double-heterojunction high electron mobility transistors (DH-HEMTs) were fabricated with an as deposited gate to compare with those with a buried gate by annealing. Instead of a recessed gate, a buried gate used to control the distance between the gate and channel (and hence the aspect ratio) improves the series resistance. Measured transconductance of 150 mS mm −1 and an open-drain voltage gain of 136 for the DH-HEMT with an as deposited gate are enhanced to 175 mS mm −1 and 160 for the DH-HEMT with a 330 • C annealed gate. Good device linearity is also obtained with a low second harmonic to fundamental ratio of 3.55%. The measured maximums f t s ( f max s) are 13.5, 13.5 and 14.5 (35, 37, and 37.5) GHz for DH-HEMTs with an as deposited gate, and with 280 • C and 330 • C annealed gates, respectively. At a measured frequency of 2.4 GHz, the DH-HEMT with a 330 • C annealed gate exhibits the highest PAE = 44.8% at V DS = 3 V and V GS = −1.0 V and the lowest F min = 1.89 dB at V DS = 3 V and I D = 200 mA mm −1 .

On the Pseudomorphic High Electron Mobility Transistors (PHEMTs) With a Low-Temperature Gate Approach

“…This result is comparable to double-heterojunction HEMTs [14] and better than the reported δ-PHEMT [6]. Device A maintains 80% of f T and f max peak values over V GS operation regimes of 0.62 V at 300 K.…”

“…This certainly causes the enhancement of output power capability. The corresponding gate current (I G ) of device A (D-mode) is 3.9 μA/mm at the gate-drain voltage of V GD = −15 V. The gate leakage current of the studied device is substantially lower than that of previously reported PHEMTs with conventionally thermal evaporated gate contacts [13], [14]. In addition, for devices with EP-gate and TE-gate, the Schottky barrier height Φ B values are 0.831 and 0.757 eV at 300 K, respectively.…”