Fully Transparent AlGaN/GaN High Electron Mobility Transistors Fabricated With Indium-Tin-Oxide Electrodes

In this letter, a fully transparent AlGaN/GaN HEMT (FT-HEMT) using indium-tin-oxide (ITO) as a transparent electrode is fabricated. The n-ohmic contacts are formed based on a Si-implant process using a deposited ITO rather than the conventional alloyed metal stacks. Following a post-annealing process at 600°C, the field-effect mobility and the maximum current density for an FT-HEMT were 1004 cm2/V·s and 179 mA/mm, respectively. Furthermore, the measured transmittance for a fabricated chip in the visible range of 400 - 700 nm was greater than 70%, which is almost the same as an as-grown GaN-on-sapphire substrate. These results show that, by using this approach, an FT-HEMT that has superior electronic properties, such as high mobility and high output current, can be realized, and show great promise for applications in transparent and/or flexible electronics, as well as other optoelectronic devices.