Temperature behavior of visible and infrared electroluminescent devices fabricated on erbium-doped GaN

Visible and infrared (IR) rare-earth-activated light emission has been obtained from Er-doped GaN electroluminescent devices (ELD). The ELD consists of an in-situ Er-doped GaN layer grown on either a sapphire or silicon (Si) substrate. The temperature dependence of the light emission and the current conduction is reported. The EL spectrum shows two main visible peaks at 537 and 558 nm and a group of closely spaced IR peaks clustered around 1550 nm. The 558 nm visible transition is dominant below 250 K, whereas the 537 nm transition is dominant at higher temperature peaking at 300 K. Temperatures from 240-500 K have minimal effect on IR emission intensity. A simple model consisting of two back-to-back Schottky diodes explains the current-voltage dependence. The effect of Er doping and substrate type on carrier transport is investigated as a function of voltage and temperature. Specifically, there is evidence that an Er-related defect is responsible for carrier generation at temperatures above 300 K. The effect of bias polarity on spatial confinement of the light emission in different areas of the devices is discussed. The model indicates that both electric field intensity and current density are important in producing light emission. The model also accounts for the uniformity of the emission under the electrodes when considering the type of substrate used for GaN:Er device growth.