【International Papers】A novel AlN/β-Ga₂O₃ high electron mobility transistor with 2 kV and 600 GHz operation

      Researchers from the Texas Tech University have published a dissertation titled "A novel AlN/β-Ga₂O₃ high electron mobility transistor with 2 kV and 600 GHz operation" in Microsystem Technologies.

Abstract

      In this work, the material characteristics of AlN and Ga₂O₃ have been exploited to develop a high-performance, AlN/Ga₂O₃ heterostructure semiconductor device to handle high-power and RF/microwave electronics applications of today’s requirement. AlN is a highly polarized ultra-wide bandgap semiconductor with a bandgap of 6.2 eV and excellent thermal conductivity. Conversely, β-Ga₂O₃, with a bandgap of 4.9 eV, is recognized as a stable ultra-wide bandgap semiconductor that is particularly well-suited for power electronics applications. However, it faces limitations such as low thermal conductivity, difficulties in achieving p-type doping, and a high density of bulk defects. However, the potential advantages of AlN and challenges of β-Ga₂O₃ can be combined by growing thin epitaxial layer of AlN over β-Ga₂O₃ to achieve high performance power electronic devices. The high 2DEG density (1.395 × 10¹⁴ cm⁻²) at the heterointerface of AlN/β-Ga₂O₃ and DC and RF characteristics up to 2 kV show the high-voltage and high-power handling capability of the device and 600 GHz cut-off frequency makes it suitable for RF/microwave applications. Unlike previous studies that report isolated performance metrics, our work presents a comprehensive analysis of barrier thickness tuning (10–100 nm), correlating it with DC, RF, and 2DEG characteristics. This provides deeper insight into optimization strategies for AlN/β-Ga₂O₃ HEMT design—a novel contribution to the current body of knowledge.

Conclusion

      The 1D Schrödinger and Poisson’s equations are self-consistently solved at the heterointerface of AlN/β-Ga₂O₃ resulting into eigen energies which shows the 2DEG formation at the heterointerface. The proposed AlN/β-Ga₂O₃ HEMT results in high 2DEG density of 1.395 × 10¹⁴ cm⁻² and high electric field of 4 MV/cm at the heterointerface. From the DC characteristics it is concluded that with the variation of AlN thickness from 10 to 100 nm the threshold voltage negatively increases from ~ 0 V to − 55 V respectively; the peak transconductance varies from 260 to 90 S respectively. However, the subthreshold slope increases from 1250 to 2500 mV/dec which suggests possible strong short-channel effects, trap-assisted conduction, or interface quality issues. The heterostructure device with AlN thickness of 100 nm conducts almost constant current of 16 A at a power supply of 2 kV at gate voltage of 3 V, which shows its potential application in very high-voltage and high-power electronics. From the frequency analysis, 600 GHz cut-off frequency (f_t) is obtained by the proposed AlN/β-Ga₂O₃ HEMT with AlN thickness of 100 nm and maximum oscillation frequency (f_max) beyond 1THz, which shows its potential capability in RF/microwave applications.