Effect of high-temperature annealing for single-Ni-layer gate in AlGaN/GaN high-electron-mobility transistors

Abstract

AlGaN/GaN high-electron-mobility transistors (HEMTs) with Schottky gate contacts are strong candidates for high-power applications with high-frequency operation. The existence of interfacial traps between Schottky gate contacts and an AlGaN surface is one of the issues causing relatively high gate leakage current in these HEMTs. High-temperature gate annealing, which reduces the density of traps owing to the interfacial reaction between Schottky gate contacts and an AlGaN surface, was investigated using a single-Ni-layer gate structure to prevent the alloying of conventional stacked metal layers such as Ni/Au and Pt/Au. As a result, a strong gate annealing temperature dependence of Schottky characteristics was observed and this dependence also caused drain current collapse. In addition, it was confirmed that 700 °C is the optimal gate annealing temperature for improving both the Schottky characteristics and drain current collapse. These results are attributed to the change in the density of interfacial trap states.

A Brief Overview of the Rapid Progress and Proposed Improvements in Gallium Nitride Epitaxy and Process for Third-Generation Semiconductors with Wide Bandgap

“…Then, the ohmic contacts were formed by depositing a Ti/Al/Ni/Au metal stack [145][146][147] and annealing at 850 • C for 30 s [148][149][150]. Next, the p-GaN gate was formed by depositing the Ni/Au metal stack and annealing at 500-800 • C [151][152][153]. Finally, the passivation layer was deposited to protect the device from environmental affecting.…”

Gate-first AlGaN/GaN HEMT technology for enhanced threshold voltage stability based on MOCVD-grown in situ SiNx

“…Comparatively, a gate stack with high immunity to HT conditions would be more beneficial for the reduction of fabrication complexity and cost [30]. Considering that the Schottky-type metal/barrier gate contact is fragile with large gate leakage and limited gate swing range, the gate contact quality could deteriorate under HT conditions [31]. Metal/insulator/semiconductor (MIS) gate stacks featuring robust dielectric insertion layer are more desirable for gatefirst GaN HEMT technology [32].…”

Ir/Al multilayer Gates for High Temperature Operated AlGaN/GaN HEMTs

“…By narrowing the Schottky gate barrier, the tunneling current is going to be dominant. Thus, suppression the density of interfacial traps between gate metal and an AlGaN surface is one of the effective methods to reduce the gate leakage current . The gate interfacial traps control the HEMT threshold voltage shift (Δ V th ) with temperature and as a consequence of this, also robustness of the HEMT for high temperature operation.…”