Hole escape processes detrimental to photoluminescence efficiency in a blue InGaN multiple-quantum-well diode under reverse bias conditions

Photoluminescence (PL) properties of a blue In0.3Ga0.7N multiple-quantum-well (MQW) diode with an additional n+-doped In0.18Ga0.82N electron reservoir layer (ERL) have been investigated at 20 K as a function of reverse bias under indirect barrier excitation. A PL intensity ratio of MQW/ERL is observed to be significantly quenched by increasing the reverse field due to electron-hole separation and carrier escape, in spite of observed blueshifts, when the excitation power is decreased by two orders of magnitude. The PL intensity reduction suggests that the hole escape process plays an important role for determination of the PL efficiency under the reverse bias

Hiroshima University's Geographical Field Researches in India : What do, how do?

海外地域調査と地誌学 : 地理学の貢献と課

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

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 In0.18Ga0.82N 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 If, i.e., large forward bias voltages Vf, 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 If, i.e., small Vf, 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