Recently, many research efforts have focused towards the development of Nitride-based semiconductor devices for various high-frequency and high-power applications. Two-dimensional device simulation allows for the analysis and optimization of these devices. For example, we evaluated the performance of transferred-electron devices based on Gunn oscillations, using our device/circuit simulator Minimos-NT.
Gunn oscillators exhibit favorable characteristics, which makes them suitable for applications like injection-locked oscillators and amplifiers. Negative Differential Mobility (NDM) is a requirement for the occurrence of the Gunn effect, which has been already extensively studied in GaAs. The frequency of oscillation of a Gunn device is determined by the time taken for a Gunn domain to form and complete the transit between the cathode and anode contacts. For this reason, it is desirable to minimize the transit time of Gunn domains, in order to achieve higher frequencies. This can be realized through a higher electron drift velocity. The wide bandgap group III-Nitride materials have several advantages, which include a large bandgap, a high breakdown field, and a high electron drift velocity. From this group, GaN has recently drawn attention, since it exhibits favorable velocity-field characteristics and can offer higher operation frequency than GaAs. In recent work, bias oscillations could be observed for a GaN Gunn diode realized on a highly doped GaN substrate. A material with even more favorable velocity-field characteristics is InN. This material offers about fifteen times higher NDM as well as about six times higher low-field mobility than GaN. However, InN has not not attracted much interest so far, most probably due to its narrower bandgap than that of GaAs. Our investigations show that both GaN and InN outperform GaAs in microwave applications. In addition, Nitride-based Gunn diodes are suitable for integration in upcoming Nitride technologies. Although GaN has attracted much interest recently, InN also offers potential advantages. Due to higher NDM, InN devices would easier fulfill the criteria for operation in the Gunn-regime, which gives them a good chance of experimental realization.