(Invited) Electrical Properties of (100) β-Ga₂O₃ Schottky Diodes with Four Different Metals

Due to its large bandgap (~4.6-4.8 eV), wide range of n-type doping, and single-crystal wafer availability, β-Ga2O3 holds promise for high-efficiency power devices. R&D of β-Ga2O3 has been conducted in Japan for more than a decade; however, funded research programs on this semiconductor material began in the U.S. only five years ago, highlighting its early stage of development. Device development of a semiconductor technology requires the ability to produce suitable ohmic and rectifying (Schottky) contacts. Whereas ohmic and Schottky contacts have been demonstrated on n-type β-Ga2O3, certain characteristics of contacts to β-Ga2O3 differ from contacts to other wide bandgap semiconductors. For example, we found that morphology was problem with many ohmic contact metals, and it was concluded that metal work function is not a dominant predictive factor for forming an ohmic contact to β-Ga2O3 [1]. Furthermore, thermal instability of the standard ohmic contact metallization (Ti/Au) is a concern for operation of devices at elevated temperatures. Schottky contacts to β-Ga2O3 have shown dependence on the orientation, growth method, and choice of metal. For example, on (-201) β-Ga2O3 Schottky barrier heights calculated from I-V measurements were typically between 0.9 and 1.3 eV and displayed little dependence on the metal work function [2]. Our preliminary measurements of selected metals on (100) β-Ga2O3 substrates yielded lower ideality factors and a correlation between barrier height and metal workfunction. The results for Schottky contacts on the (100) surface show some similarities to those previously reported on the (010) surface. In this presentation specific examples of ohmic and Schottky contact metallizations to β-Ga2O3 will provide a platform for more detailed discussion. [1] Y. Yao, R.F. Davis, and L.M. Porter, J. Electron. Mater. 46(4), 2053-2060 (2016). [2] Y. Yao, R. Gangireddy, J. Kim, K. Das, R.F. Davis, and L.M. Porter, J. Vac. Sci. Technol. B 35(3), 03D113.1-7 (2017).