Changes in electron and hole traps in GaN-based light emitting diodes from near-UV to green spectral ranges

Abstract

Deep electron and hole traps were studied by admittance spectroscopy (AS) and deep level transient spectroscopy (DLTS) with electrical and optical (ODLTS) injection for GaN-based multi-quantumwell (MQW) light emitting diodes (LEDs) operating in the near-UV (385-390 nm), blue (445 nm), and green (515 nm) spectral regions. AS spectra were dominated by freezing out of Mg acceptors at temperatures around 150K, by shallow centers in the MQW region, and, for green LEDs, by deeper electron traps with a level near E-c - 0.27 eV located in the MQW region. DLTS spectra showed electron traps with levels E-c - 0.8 eV (NUV), E-c - 0.5 eV (blue), E-c - 0.6 eV (blue and NUV), and E-c - 0.27(green LEDs). In ODLTS, hole traps near E-v + 0.75 eV (NUV), E-v + 0.65 eV (blue), and E-v + 0.45 eV (green LEDs) originating in the quantum well (QW) region were detected (the QW character was confirmed by using excitation light that generated electron-hole pairs only within the QWs). The levels of the electron and hole traps in LED structures differing in the In composition in the QWs were well aligned with respect to the vacuum level. Published by AIP Publishing.