Defects in the active layer p-Al0.35Ga0.65As of high-brightness red-light-emitting diodes

Abstract

The authors studied defect states introduced in the Zn-doped AlGaAs active layer of high-brightness red-light-emitting diodes with double heterostructure (DH-LEDS) fabricated by liquid phase epitaxy (LPE) with a sliding boat and determined the correlation between LED brightness and deep levels due to defects in the active layer. Deep levels comprising a majority carrier (hole) trap and two minority carrier (electron) traps have been observed by capacitance transient spectroscopies (DLTS and ICTS). The correlation that DH-LEDS with a lower density of deep levels exhibit a higher radiative efficiency has been revealed by measurements of the brightness and by scanning ICTS (SICTS). A unique pattern of high- or low-intensity regions perpendicular to the sliding direction has been observed in both the spatial distribution of the brightness and the density of deep levels. Furthermore, by using DH-LEDS fabricated by LPE without the sliding boat, it has been revealed that the introduction of deep levels depends on the crystal growth process. These experimental results suggest that the unique distribution pattern observed in the brightness and the density of deep levels is introduced by fluctuations of the interface at the p-n junction caused by melt carry-over in the sliding boat method.