COMPARISON OF SINGLE-HETEROSTRUCTURE AND DOUBLE-HETEROSTRUCTURE ALGAAS/INGAP RED LIGHT-EMITTING-DIODES PREPARED BY LIQUID-PHASE EPITAXY

The performance of the AlGaAs/InGaP single-heterostructure (SH) and AlGaAs/InGaP/AlGaAs double-heterostructure (DH) light-emitting diodes (LEDs) is compared. For these two types of LEDs, they have a very shining surface morphology and flat interface. However, the SH LEDs always exhibit better properties than the DH LEDs in the ideality factor, electroluminescence, light output power, and external quantum efficiency. From the x-ray diffraction measurements, we find that the main problem for the undesirable performance of DH LEDs is attributed to the difficulty of obtaining the high quality InGaP/AlGaAs heterostructure. Furthermore, by the Auger-depth-profile measurements, it is found that the P atoms with a very high diffusivity will diffuse into the as-grown AlGaAs layer during the growth of InGaP and thus destroy the heterostructure quality.