High Performance InAlN/GaN/Si High Electron Mobility Transistor Using Microwave Ohmic Annealing Technique

Abstract

In this study, a high-performance InAlN/GaN high electron mobility transistor (HEMT) was fabricated using low-temperature microwave annealing (MWA) as the ohmic metal alloy process for the first time. Ni-Al alloy aggregation is significant for InAlN devices because of the high Al fraction in InAlN layer. Furthermore, the indium segregation and out-diffusion of the InAlN barrier layer resulted in lower drain current and the formation of extra trap centers. Compared with traditional rapid thermal annealing with a high-temperature process window, MWA results in simultaneously superior ohmic contact and wafer sheet resistances because of the superior surface morphology of the ohmic metal alloy in the MWA device. Moreover, the heterostructure interfacial quality of two-dimensional electron gas density can be maintained through low-temperature MWA, as indicated by reciprocal space map measurements. Furthermore, Baliga's figure-of-merit calculation indicated that the MWA-InAlN HEMT had superior DC characteristics, providing improved device radiofrequency bandwidth and output power density performance.

Improved RF power performance of InAlN/GaN HEMT by optimizing rapid thermal annealing process for high-performance low-voltage terminal applications

“…[12,22,23] However, compared with the non-optimized RTA sample, the optimized one has smoother ohmic metal surface morphology whose rootmean-square (rms) surface roughness and maximum height variation of bulges (∆H) are obviously reduced, which is attributed to the less Ni-Al alloy aggregation by relatively lower RTA temperature. [12,21] Besides the evaluation of the degradation for heterojunction sheet resistance mentioned above, another heterojunction quality of both samples is compared in Fig. 4.…”

“…[16] Thus, device fabrication should be performed on a more strongly polarized heterojunction with low sheet resistance, such as an InAlN/GaN heterojunction. [17,18] On the basis of an InAlN/GaN heterojunction, the RTA process must be carefully designed because both the higher RTA temperature and longer time will cause the rough ohmic metal surface morphology and degraded heterojunction quality to induce a series of negative effects on device performance and reliability, [19][20][21] in spite of the lower ohmic contact resistance (R C ). As a consequence, for the InAlN/GaN heterojunction, it is vital to optimize the RTA condition and explore the appropriate one, which may be different from the optimal annealing condition for a conventional AlGaN/GaN heterojunction.…”