High‐Current‐Density Enhancement‐Mode Ultrawide‐Bandgap AlGaN Channel Metal–Insulator–Semiconductor Heterojunction Field‐Effect Transistors with a Threshold Voltage of 5 V

Abstract

Enhancement‐mode ultrawide‐bandgap Al0.65Ga0.35N/Al0.4Ga0.6N metal–insulator–semiconductor heterojunction field‐effect transistors are demonstrated using fluorine‐plasma treatment for threshold voltage control and Al2O3 as gate dielectric. The device exhibits a threshold voltage of 5 V, a maximum drain current density of 105 mA mm−1, and a transconductance of 19 mS mm−1. In addition, the capability to achieve low off‐state current density at 3–4 × 10−9 mA mm−1, an exceptionally low gate leakage current density of 1.4 × 10−8 mA mm−1 even at a high forward gate bias of VGS = 12 V, and a current on/off ratio >1010 is shown. Small signal measurement shows that the device has a unity current gain cutoff frequency fT of 3.8 GHz and power gain cutoff frequency fmax of 4.5 GHz.

From wide to ultrawide-bandgap semiconductors for high power and high frequency electronic devices

“…In 2020, Xue et al reported an Al 0.65 Ga 0.35 N/Al 0.4 Ga 0.6 N HEMT with a current density of 900 mA mm −1 , f T of 20 GHz, and f max of 36 MHz. The off-state breakdown voltage in these devices was 80 V with 1 µm gate to drain separation and a gate length of 100 nm [217]. The same group demonstrated an exceptionally low gate leakage current density of 1.4 × 10 −8 mA mm −1 even at a high forward gate bias of V GS of 12 V, and a current on/off ratio >10 10 was achieved simultaneously.…”

“…The same group demonstrated an exceptionally low gate leakage current density of 1.4 × 10 −8 mA mm −1 even at a high forward gate bias of V GS of 12 V, and a current on/off ratio >10 10 was achieved simultaneously. Small signal measurement showed that the device has an f T of 3.8 GHz and f max of 4.5 GHz for the same Al compositions [245]. The RF operation of AlGaN channel transistor with Al-composition above 80% was first reported in 2018 demonstrating an impressive current density of 265 mA mm −1 for a gate length of 0.8 µm.…”

“…Following the realization of high-quality GaN grown on low-temperature AlN buffer layers in 1986 [46], the growth of AlGaN and AlGaN/GaN heterojunctions gained significant attention over the past three decades with vast application prospects in high temperature, high power, RF, and optoelectronic devices [214][215][216][217]. AlGaN films were first grown as buffer layers for the growth of GaN or AlN epilayers.…”

“…State-of-the-art RF performance: (a) fmax vs f T and (b) Pout vs frequency of U/WBG transistors. References for (a) GaN HEMTs: [490-501]; AlGaN: [217, 242-248, 502]; diamond: [321-324, 503-510]; Ga2O3: [444, 448, 449, 511] and (b) GaNHEMTs:[157, 159, 160, 164-166, 171, 176, 178, 490, 512]; AlGaN:[217,242,247,248]; diamond:[319, 320, 322, 324, 503-508, 325,513,514]; Ga2O3[444][445][446].…”