- Hole gas boost for deep UV diode wall-plug efficiency
- Semiconductor Today
US-based Bolb Inc and Semicon Light Co of South Korea have increased efficiency and reduced forward voltage for 280nm-wavelength deep ultraviolet (DUV) light-emitting diodes by creating a two-dimensional hole gas at the p-contact surface using variously strained layers of magnesium (Mg)-doped aluminium gallium nitride (AlGaN) [Jianping Zhang et al, Semicond. Sci. Technol., vol33, p07LT01, 2018]. The hole gas was formed at the surface of a strained heavily doped AlN layer due to strong polarization electric fields, which raised the valence band states above the Fermi level. The electric field arises from the spontaneous charge polarization of the III(Al,Ga)–nitride bond. An added component to the field comes from strain-dependent piezoelectric effects.