The high sheet-carrier density of the two-dimensional electron-gas (2-DEG) [1, 2] and large critical breakdown electric field [3, 4] allow the fabricated HEMT devices with unprecedented high drain current density and large breakdown voltage, which are essential for the important applications of power devices [5–9]. However, the high sheet electron density inherently in GaN-based HEMTs will inevitably induce the spillover of transport electrons at high-drain-voltage conditions, and that becomes a growing issue. In general, the confinement of transport electrons to Daporinad nmr the bottom side of the device is insufficient in the conventional AlGaN/GaN HEMT, due mainly to the insufficient potential height
provided by the GaN buffer layer underneath. Consequently, transport electrons supposed to be confined within the 2-DEG channel would easily spill or leak into the buffer layer, causing a rapid increase of subthreshold drain leakage currents, accelerating the device breakdown. The above-mentioned phenomenon is often interpreted as the ‘punchthrough effect,’ hindering the further ALK inhibitor applications of GaN-based HEMTs. Therefore, methods improving the confinement of transport electrons
within the channel layer and alleviating the punchthrough effect are necessary. Over the years, several approaches, such as the introduction of p-type doping to the GaN buffer layer [10–12] and the use of AlGaN/GaN/AlGaN double-heterojunction HEMTs [13–15], have been reported to enhance the breakdown voltage of GaN-based HEMTs. The basic principle is
to raise the conduction band of the GaN buffer layer, and thus generates a deeper and narrower potential well for the better confinement of 2-DEG. In this SPTLC1 work, we present an improved bottom confinement of 2-DEG by introducing the AlGaN/GaN/AlGaN quantum-well (QW) electron-blocking layer (EBL) structure. It is shown that the large electric field induced at the interfaces of AlGaN/GaN/AlGaN QW EBL effectively depletes the spilling electrons toward the 2-DEG channel. As compared to previous approaches, the subthreshold drain leakage current becomes less sensitive to the drain voltage (V ds), and that postpones the HEMT breakdown. Meanwhile, our proposed structure not only exhibits the highest electron mobility among other compared HEMT devices but also allows a great tolerance for epitaxial imperfections during the device fabrication. As a result, we conclude that the proposed AlGaN/GaN/AlGaN QW EBL HEMT is viable and highly promising for the high-speed and high-power-switching applications. Methods For comparison, four types of devices were numerically studied and the schematic structures are plotted in Figure 1. All devices are designed on an insulating sapphire substrate and have a 40-nm-thick AlN nucleation layer followed by an un-doped GaN buffer layer with a thickness of 1.5 μm.