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The AlGaN‐channel III‐N heterostructure effect transistor (HFET) devices with high breakdown voltage and acceptable on‐resistance has shown great potential for next generation of power switching. The electronic transport property of two‐dimensional electron gases (2DEGs) in AlInGaN/AlGaN heterostructures is investigated for the first time, and the effects of the alloy disorder scattering from both the barrier layer and the channel layer are analyzed. The quaternary alloy composition dependences of the 2DEG density and mobility and the sheet resistance (positively proportional to the device on‐resistance) are studied in nearly lattice matched AlInGaN/Al0.2Ga0.8N heterostructures. The alloy composition ranges of the AlxInyGa1−x−yN barrier layer of 0.58 ≤ x ≤ 0.76 and 0 ≤ y ≤ 0.14 is found to be optimal in all aspects, which corresponds to the threshold voltage of −1.55 ∼ −6.24 V for an AlInGaN/Al0.2Ga0.8N HFET with a nickel gate. Moreover, the temperature dependence of 2DEG mobility in lattice‐matched AlInGaN/AlGaN heterostructures is discussed with various scattering models. The results show that the magnitudes of the mobility in the sample Al0.3In0.05Ga0.65N/Al0.05Ga0.95N, Al0.5In0.06Ga0.44N/Al0.2Ga0.8N, and Al0.8In0.06Ga0.14N/Al0.5Ga0.5N heterostructures reduces by 61%, 47%, and 37% with the temperature increasing from 300 to 600 K. Our research may provide some instructions for the application of AlInGaN/AlGaN heterojunction to high voltage power devices.

We established the model of the electron mobility limited by the alloy composition fluctuation scattering in the quaternary AlxInyGa1-x-yN/GaN heterojunctions for the first time. The alloy composition fluctuation along the AlxInyGa1-x-yN/GaN heterointerface was considered and characterized by the lateral correlation length L, and the fluctuations of aluminum and indium mole fractions (Δx and Δy) independent to each other. The situation of alloy composition fluctuation is investigated in the following cases. Only x or y fluctuates, and both x and y fluctuate with equal/unequal amplitudes in the same/opposite direction. We find that the scattering with both x and y fluctuating in the same direction is the weakest, while x and y fluctuating in the opposite directions leads to the strongest scattering. This in nature stems from the disparity of the bandgap and polarization in AlInN, AlGaN and GaN. The effects of different parameters, such as x and y, Δx and Δy, L, and the thickness of AlxInyGa1-x-yN barrier layer d on the mobility are also studied. The model will in principle give a universal explanation to the effect of alloy composition fluctuation scattering on the carrier mobility in the GaN-based heterostructures with ternary or quaternary alloy barrier layers.

GaN-based heterostructures with an InAlGaN/AlGaN composite barrier on sapphire (0001) substrates are grown by a low-pressure metal organic chemical vapor deposition system. Compositions of the InAlGaN layer are determined by x-ray photoelectron spectroscopy, structure and crystal quality of the heterostructures are identified by high resolution x-ray diffraction, surface morphology of the samples are examined by an atomic force microscope, and Hall effect and capacitance-voltage measurements are performed at room temperature to evaluate the electrical properties of heterostructures. The Al/In ratio of the InAlGaN layer is 4.43, which indicates that the InAlGaN quaternary layer is nearly lattice-matched to the GaN channel. Capacitance–voltage results show that there is no parasitic channel formed between the InAlGaN layer and the AlGaN layer. Compared with the InAlGaN/GaN heterostructure, the electrical properties of the InAlGaN/AlGaN/GaN heterostructure are improved obviously. Influences of the thickness of the AlGaN layer on the electrical properties of the heterostructures are studied. With the optimal thickness of the AlGaN layer to be 5 nm, the 2DEG mobility, sheet density and the sheet resistance of the sample is 1889.61 cm2/V · s, 1.44 × 1013 cm−2 and as low as 201.1 ω/sq, respectively.

In this paper, we propose a near-infrared p-type β -FeSi 2 /n-type 4H-SiC heterojunction photodetector with semiconducting silicide (β -FeSi 2 ) as the active region for the first time. The optoelectronic characteristics of the photodetector are simulated using a commercial simulator at room temperature. The results show that the photodetector has a good rectifying character and a good response to near-infrared light. Interface states should be minimized to obtain a lower reverse leakage current. The response spectrum of the β -FeSi 2 /4H-SiC detector, which consists of a p-type β -FeSi 2 absorption layer with a doping concentration of 1 × 10 15 cm −3 and a thickness of 2.5 µm, has a peak of 755 mA/W at 1.42 µm. The illumination of the SiC side obtains a higher responsivity than that of the β -FeSi 2 side. The results illustrate that the β -FeSi 2 /4H-SiC heterojunction can be used as a near-infrared photodetector compatible with near-infrared optically-activated SiC-based power switching devices.