Equations for the Electron Density of the Two-Dimensional Electron Gas in Realistic AlGaN/GaN Heterostructures

This paper presents equations for the electron density of the two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructures in three realistic scenarios: (1) AlGaN/GaN heterostructure with surface exposed to ambient with mobile ions, (2) metal gate deposited on the AlGaN surface, and (3) a thick dielectric passivation layer on the AlGaN surface. To derive the equations, we analyzed these scenarios by applying Gauss’s law. In contrast to the idealistic models, our analysis shows that the 2DEG charge density is proportional to the difference between spontaneous polarization of AlGaN and GaN, whereas surprisingly, it is independent of the piezoelectric polarization.

A novel AlGaN/GaN heterostructure field-effect transistor based on open-gate technology

In this study, a novel AlGaN/GaN heterostructure field-effect transistor based on open-gate technology was fabricated. Sample transistors of different structures and sizes were constructed. Through measurements, it was found that by changing the width of the opening, the threshold voltage of the device could be easily modulated across a larger range. The open-gate device had two working modes with different transconductance. When the gate-source voltage VGS ≤ − 4.5 V, only the open region was conductive, and a new working mechanism modulated the channel current. Corresponding theoretical analysis and calculations showed that its saturation mechanism was related to a virtual gate formed by electron injection onto the surface. Also, the gate-source voltage modulated the open channel current by changing the channel electron mobility through polarization Coulomb field scattering. When used as class-A voltage amplifiers, open-gate devices can achieve effective voltage amplification with very low power consumption.

Influence of AlN/GaN interfacial non-idealities on the properties of two-dimensional electron gas in AlGaN/AlN/GaN heterostructures

The influence of two types of AlN/GaN interfacial non-idealities, namely unintentional Ga incorporation into AlN spacer and blurring of the spacer due to Al and/or Ga atomic diffusion on the mobility and density of two-dimensional electron gas in AlGaN/AlN/GaN heterostructure was studied theoretically. It was found that moderate amount of GaN in the nominal AlN spacer does not affect much the mobility and density of 2DEG as long as the interface is abrupt. In contrast, the blurring of AlN/GaN interface was found to have a significant impact on the mobility and sheet resistance of the structure since the GaN channel actually becomes AlGaN and alloy-disorder scattering takes place.

Analysis of Thermal Characteristics of AlGaN/GaN Heterostructure Field-Effect Transistors Using Micro-Raman Spectroscopy

We investigated the heat dissipation in heterostructure field-effect transistors (HFETs) using microRaman measurement of the temperature in active AIGaN/GaN. By varying the gate structure, the heat dissipation through the gate was clearly revealed. The temperature increased to 120 °C at the flat gate device although the inserted gate increased to only 37 °C. Our results showed that the inserted gate structure reduced the self-heating effect by three times compared to the flat gate structure. Temperature mapping using micro-Raman measurement confirmed that the temperature of the near gate area was lower than that of the near drain area. This indicated that the inserted gate electrode structure effectively prohibited self-heating effects.

High Performance Broadband Ultraviolet A/Ultraviolet C Detector Based on Ga2O3/p-GaN Nanocomposite Film Fabricated by Magnetron Sputtering

Ultraviolet (UV) detector based on β-Ga2O3/p-GaN was fabricated in this paper. The growth process involved deposition of amorphous Ga2O3 layer by means of magnetron sputtering and conversion of β-Ga2O3. The obtained detector displays excellent UV sensing properties which covers Ultraviolet A(UVA)/Ultraviolet C(UVC) region with fast response. It will provide a new route to fabricate β-Ga2O3/p-GaN heterostructure for applications in broadband ultraviolet sensing.