660-V/1.99-mΩ.cm2 Low-Current-Collapse p-GaN/AlGaN/GaN HEMTs With Selective Regrowth AlN/AlGaN Strain Layers

In this article, an enhancement mode (E-mode) p-GaN gate AlGaN/GaN high electron mobility transistor (HEMT) with the selective regrowth (SR) AlN/AlGaN strain enhancement layers has been proposed. The novel strain engineering is used to realize 2-D electron gas (2DEG) redistribution by the polarization effect and surface electric field optimization by the electric field modulation effect. The SR AlN/AlGaN strain layers increase the 2DEG density in the access region to reduce the ON-resistance ( {R}_{\text {on}}{)} effectively. The surface electric field is also reshaped, featuring an extra electric field peak far away from the gate edge, which improves the breakdown voltage (BV). As compared with the conventional HEMT, the HEMT with the SR AlN/AlGaN strain layers features the significant specific ON-resistance ( {R}_{\text {on, sp}}{)} improvement by 11.9% (from 2.26 to 1.99 \text{m}\Omega {\mathrm {.cm}}^{{2}}{)} and the noticeable BV enhancement from 476 to 661 V. It is concluded that the contradiction between {R}_{\text {on, sp}} and BV can be relieved by using the SR AlN/AlGaN strain layers. Meanwhile, the current collapse is suppressed effectively. The dynamic {R}_{\text {on}} is only 1.3 times the static {R}_{\text {on}} after the drain-source OFF-state stress of 480 V.