CARRIER CAPTURE AND RECOMBINATION AT LOCALIZED STATES IN InGaN/GaN LIGHT-EMITTING DIODES

摘要

Temperature-dependent electroluminescence (EL) of InGaN/GaN multiple-quantum-well (MQW) light-emitting diodes (LEDs) with identical structure but varying degrees of indium in the active region has been investigated to illustrate the role of localization effects in carrier capture and recombination. In the UV and blue LEDs, a large redshift of the emission peak in the range of 20-50 meV with decreasing temperature from 200 K to 77 K is observed, accompanying a pronounced decrease of the EL intensity. This behavior can be explained by carrier relaxation into lower energy states, yielding the dominant radiative recombination mechanism to carriers captured by localized states. In contrast, the emission energy of the green LED was minimally affected by temperature, and the emission intensity increased monotonically with decreasing temperature down to 5 K. The dominant radiative recombination in this LED is attributed to efficient carrier capturing by a large number of localized states in the MQW region.