Investigation of Peak-to-Valley Current Ratio of GaN/AlN Resonant Tunneling Diodes

Peak-to-valley current ratios (PVCRs) achie-ved in GaN/AlN resonant tunneling diodes (RTDs) are less than 2, significantly less than their counterparts, such as InGaAs/AlAs RTDs (e.g., PVCR $\sim$ 12). This has hindered their high-speed applications because the maximum self-oscillation frequency and minimum switching time generally increase and decrease with PVCR. In this article, we investigate the problem of low PVCR in GaN/AlN RTDs with both modeling and experiments. Firstly, we developed a Schrodinger equation-based solver for RTD simulations. While the solver gives reasonable agreement with the experimental current-voltage (I-V) characteristics, such as the positions of resonant peaks, it predicts a much higher PVCR. Then, we conducted temperature dependence studies on GaN/AlN RTDs and compared them with InGaAs/AlAs RTDs. The similarities observed suggest that sequential tunneling with phase randomization, resulting from scattering processes such as optical phonon and interface roughness scattering, is responsible for the large valley currents in GaN/AlN RTDs.