Han-Chieh Ho

Device Characteristics of InGaSb/AlSb High-Hole-Mobility FETs

This letter reports the effect of growth temperature on carrier transport characteristics in In_0.4Ga_0.6Sb/AlSb heterostructure and demonstrates that hole mobility was enhanced by eliminating a parallel conducting channel in the buffer layers. Based on optimized growth conditions, hole mobility as high as 1220 cm²/V·s with carrier concentration of 1.3 ×10¹² cm^-2 was achieved. A 0.2- μm-gate-length In_0.4Ga_0.6Sb/AlSb p-channel device exhibited a maximum drain current of 102 mA/mm, a peak transconductance of 92 mS/mm, and an on-state breakdown voltage over 3 V. The pinchoff was observed for a gate bias of 0.6 V at drain current of 1 mA/mm. The current-gain and power-gain cutoff frequencies were 15 and 20 GHz, respectively.

Effect of Gate Length on Device Performances of AlSb/InAs High Electron Mobility Transistors Fabricated Using BCl3 Dry Etching

In this paper, we present the development of a mesa isolation process for AlSb/InAs high electron mobility transistors (HEMTs) using inductively coupled plasma (ICP) etching with BCl3 gas. Devices with different gate lengths (Lg: 60, 100, and 200 nm) fabricated by this dry etching technique show good DC and RF performances. With an appropriate Lg/gate-channel distance ratio, the 200-nm-gate has very high peak transconductances of 781 mS/mm at VDS = 0.1 V and 2000 mS/mm at VDS = 0.5 V. Moreover, an extrinsic current gain cutoff frequency of 137 GHz and maximum oscillation frequency of 97 GHz were achieved at a drain bias voltage VDS = 0.3 V, indicating the great potential for such a device operating at high frequency with extremely low DC power consumption.

DC and RF characteristics of InAs-channel MOS-MODFETs using PECVD SiO 2 as gate dielectrics

Small-bandgap InAs channel materials are potential candidates for high-speed and low-power applications and have been demonstrated in AlSb/InAs/AlSb QWFETs. Taking advantage of their excellent transport properties, we successfully develop an InAs-channel metal-oxide-semiconductor modulation-doped field-effect transistor (MOS-MODFET) using 100-nm PECVD-deposited SiO2 dielectrics for gate dielectrics. A 2µm-gate-length depletion-mode InAs n-channel MOS-MODFET shows a maximum drain current of 270 mA/mm, a peak transconductance of 189 mS/mm, and a low output conductance of 18 mS/mm in dc characteristics, and a maximum current-gain cut-off frequency of 14.5 GHz and a maximum oscillation frequency of 24.0 GHz in rf performances. The InAs-channel MOS-MODFET presents potentials for further developing complementary circuit devices.

Ti- and Pt-based Schottky gates for InGaSb p-channel HFET development

Antimonide-based heterostructural p-channel HFET epitaxies consisting of an In0.44Ga0.56Sb quantum well located between AlSb barriers were developed by molecular beam epitaxy. The In0.44Ga0.56Sb channel layer was compressively strained to enhance hole mobility. Room-temperature Hall measurements to the as-grown materials exhibited a hole mobility as high as 895 cm2/V s. Ti/Pt/Au and Pt/Ti/Pt/Au metals were utilized in Schottky gate metallization processes for evaluating their effects on the device performance. Considering the diffusivity of Pt metals, the devices with as-deposited and annealed Pt-based gates were characterized simultaneously and compared with the ones with Ti-based gates. The devices with Ti-based gates yielded superior dc and rf performances to those with Pt-based gates.