Electro-thermal co-design of β-(Al_xGa_(1-x))_2O_3/Ga_2O_3 modulation doped field effect transistors

摘要

Ultra-wide bandgap β-gallium oxide (Ga_2O_3) devices are of considerable interest with potential applications in both power electronics and radio frequency devices. However, current Ga_2O_3 device technologies are limited by the material's low intrinsic electron mobility and thermal conductivity. The former problem can be addressed by employing modulation-doped β-(Al_xGa_(1-x))_2O_3/Ga_2O_3 heterostructures in the device architecture. In this work, (Al_xGa_(1-x)))2O_3/Ga_2O_3 modulation-doped field effect transistors (MODFETs) have been investigated from a thermal perspective. Thermoreflectance thermal imaging was used to characterize the self-heating of the MODFETs. The (Al_(0.18)Ga_(0.82))_2O_3 thermal conductivity (3.1-3.6 W/mK) was determined using a frequency domain thermoreflectance technique. Electro-thermal modeling was used to discern the effect of design parameters such as substrate orientation and channel length on the device self-heating behavior. Various thermal management schemes were evaluated using the electro-thermal device model. From an electro-thermal co-design perspective, the improvement in electrical performance followed by the mitigation of self-heating was also studied. For example, by employing a Ga_2O_3-on-SiC composite wafer, which was fabricated in this work, a 50% increase in power handling capability can be achieved as compared to a homoepitaxial device. Furthermore, flip-chip heterointegration and double-sided cooling approaches can lead to more than 2 × improvement in the power handling capability. Using an augmented double-sided cooling design that includes nanocrystalline diamond passivation, a 5 x improvement in the power handling capability can be accomplished, indicating the potential of the technology upon implementation of a suitable thermal management scheme.