Electroluminescence efficiency of blue InGaN/GaN quantum-well diodes with and without an n-InGaN electron reservoir layer

摘要

The temperature dependence of the electroluminescence (EL) spectral intensity has been investigated in detail between T=20 and 300 K at various injection current levels for a set of two blue InGaN/GaN multiple-quantum-well (MQW) light-emitting diodes (LEDs) with and without an additional n-doped In_(0.18)Ga_(0.82)N electron reservoir layer (ERL). The radiative recombination efficiency of the main blue emission band (～480 nm) is found to be significantly improved at all temperature regions and current levels when the additional ERL is introduced. For high injection currents I_f, i.e., large forward bias voltages V_f, a quenching of the EL intensity is observed for T < 100 K for both LED structures, accompanying appearance of short-wavelength satellite emissions around 380-430 nm. Furthermore, the low-temperature intensity reduction of the main EL band is stronger for the LED without the ERL than with the ERL. For low I_f, i.e., small V_f, however, no quenching of the EL intensity is observed for both LEDs even below 100 K and the short-wavelength satellite emissions are significantly reduced. These results of the main blue emission and the short-wavelength satellite bands imply that the unusual evolution of the EL intensity with temperature and current is caused by variations of the actual potential field distribution due to both internal and external fields. They significantly influence the carrier capture efficiency by radiative recombination centers within the active MQW layer and the carrier escape out of the active regions into high-energy recombination centers responsible for the short-wavelength satellite emissions.