Polarization-engineered N-face III–V nitride quantum well LEDs

Abstract

III–V nitride semiconductors are direct band gap semiconductors spanning a wide range of band gaps from 0.7 eV (InN, IR), through 3.4 eV (GaN, UV) to 6.2 eV (AlN, deep UV). This makes them uniquely suited for fabricating visible and UV LEDs [1]. UV LEDs have applications in water purification, microscopy and chemical analysis. However, wide band gap nitrides suffer from poor p-type doping owing to large activation energy of Mg acceptor dopant ( EA∼200 meV for GaN [2] and 650 meV for AlN [3]). This results in low thermal activation of holes at room temperature and causes low p-type conductivity. III–V nitrides also exhibit large built-in polarization field with spontaneous and strain induced piezoelectric components [4]. The polarization has recently been exploited to demonstrate N-face AlGaN/GaN p-n heterojunctions with improved p-type conductivities and electroluminescence [5]. In this work, we demonstrate that incorporating quantum wells (QWs) into the active regions improves electroluminescence (EL). Simultaneously, a number of advantages of N-face structures emerge from the point of view of polarization-engineering.