Photocurrent characteristics of two-dimensional-electron-gas-based AlGaN/GaN metal-semiconductor-metal photodetectors

Photocurrent response characteristics of two-dimensional-electron-gas-based AlGaN/GaN metal-semiconductor-metal (MSM) photodetectors were investigated by changing the frequency of incident light signals. At low chopper frequencies, the contribution to the photocurrent is mainly from the GaN bulk layer at 5 V bias, as expected. With increasing chopper frequency, a peak response at 361 nm wavelength becomes more and more pronounced and dominates gradually the photocurrent spectrum, indicating that this peak response has a much less frequency dependence and a faster response rate than the spectral response from the GaN bulk layer. This peak response is attributed to the contribution of photoelectrons generated in the two-dimensional electron gas (2DEG) channel according to simulation results of electrical field distribution and analysis of carrier transport in the 2DEG-based AlGaN/GaN heterostructure. This characteristic makes the 2DEG-based MSM photodetectors a large potential to develop high-speed ultraviolet optoelectronic integrated devices with AlGaN/GaN high electron mobility transistors.