Reproducible High-Efficiency GaP Green-Emitting Diodes Grown by Overcompensation

Abstract

High-effciency GaP green light-emitting p-n junctions have been reproducibly grown employing an overcompensation technique in a vertical dipping LPE system. In this technique b~th the n-and p-type layers are grown in a single LPE crystal growth run, eliminating potential interface problems at the junction. For junction material grown at an initial temperature of 900~ the EL quantum effciencies of encapsulated mesa diodes ranged from 0.08 to 0.14% and averaged 0.10% at 5 mA (,~5-10 A/cm2). Minority carrier diffusion lengths (L~Lh) and relative cathode-luminescence efficiency (CL) were measured in a scanning electron microscope. At excitation levels equivalent to current densities of ,~1-10 A/cm2 in a p-n junction, both Le and Z,h range from 3 to 5~ with maximum measured values of Lh = 7.2# and Le --5.6/~ for material grown from 900~ At the same excitation level the CL efficiency of the p-layers was typically found to be approximately 2-3 times that of the n-layers. Typical values for Le, Lh, CL, and the EL effciencies were found to be larger by --,50% for material grown from 900~ compared to similarly grown material from 1000~The major assets of the overcompensation technique are the high degree of reproducibility in obtaining high effciencies and that only a single growth process is necessary to form the p~ junction.

Very High Efficiency GaP Green Light Emitting Diodes

“…The LPE layers were grown in an open flow dipping system which has been in continual use in the GaP green LED optimization program (1)(2)(3). The new growth cycle (5), hereafter termed "modified," adopted for this work incorporates a number of procedural changes from the "overcompensation" procedure (1) used previously.…”

“…The ambient gas consists of H2 plus 1.5 • 10 -~ arm of NH3 which is unchanged from that used previously. This ammonia addition to the gas stream results in a N concentration in the GaP of 2 • 1,0 'is cm -a as measured by optical absorption (1,4,8). Since the n-layer is not deliberately doped, the resulting net donor concentration varied considerably, viz., ~ 5 • 10 ,1~ < (Nd-Na) ~ 1 X 101~ cm -8.…”

“…A considerable effort has been devoted over the past three years to improving the quantum efficiency of GaP green light emitting diodes (LED's) and to understand the operation of the device (1,2). As a result of this work p-n junction material has been reproducibly grown with electroluminescent (EL) quantum efficiencies of encapsulated mesa diodes averaging 0.1% at 5 A/cm 2 (1).…”

“…The overcompensation procedure used to obtain these efficiencies (1) was one where both the n-and p-layers were grown in a single run. A Te,N doped nlayer was first grown by cooling the melt from 900 ~ to 880 ~ or 870~…”

Oxygen Gettering in Green GaP : N LED's Grown by Overcompensated LPE

“…It has been our experience as that of Lorimor at 2.310 eV at 77~ (24,25). The results are listed in et al (6) that epilayers grown by overcompensation Table III. Diode efficiency.--The external EL quantum efficiency of various diodes was determined on fabricated structures which had an evaporated contact similar to the one described by Schumaker et al (26) for red LED's.…”