In this study, a 50-nm Al_0.05Ga_0.95N back barrier (BB) layer was used in an AlGaN/GaN high-electron-mobility transistor between the two-dimensional electron gas channel and Fe-doped/C-doped buffer layers. This BB layer can reduce the channel layer. The BB layer is affected by doped carriers in the buffer layer and the conduction energy band between the channel and the buffer layers. The I_on/I_off ratio of the BB device was 3.43 × 10⁵ and the ratio for the device without BB was 1.91 × 10³. Lower leakage currents were obtained in the BB device because of the higher conduction energy band. The 0.25-μm gate length device with the BB exhibited a high current gain cutoff frequency of 26.9 GHz and power gain cutoff frequency of 54.7 GHz.

In this study, AlGaN back barriers (B.B.) with different Al mole fractions and thicknesses were used in AlGaN/GaN high electron mobility transistors (HEMTs) to improve device performance. Relative to thickness, a proper Al mole fraction (Al_0.08GaN) of the B.B. more strongly affected the device’ I_on/I_off ratio. It exhibited a low leakage current and high I_on/I_off ratio of approximately 10⁶. Relative to B.B. mole fraction, B.B. thickness more greatly affected the devices’ horizontal breakdown voltage (760V) and LFN characteristics. Increasing the Al mole fraction and the thickness of the B.B. more strongly affected the dynamic R_ON. The current gain cut-off frequency (f_T) and maximum stable gain cut-off frequency (f_max) were 5.2 GHz and 10.5 GHz, respectively, for the Al_0.08GaN B.B. device.

18.16.2023_Huang V1 with Marty edits all accepted