Light generation in diffused GaP light emitting diodes (LEDs)
Abstract
The results of a programme of research on nitrogen doped green-emitting diffused VPE LEDs are reported. The purpose of this work was to establish whether the recombination processes which control final device efficiencies occur on the p or n side of the junction. To do this we have used a novel technique which involves fabricating diodes down a bevelled epitaxial "sandwich" structure consisting of a nitrogen doped region between non nitrogen doped ones. We find that the light output from the n side is approximately a factor 1.5 times the p side output. Hence both the p and n regions of these diffused structures yield significant light outputs, although the contribution from the n side usually dominates. The above result together with cathodoluminesence efficiency measurements on p- and n-type material suggests the device injection ratio (β), defined as the ratio of injected hole and electrom currents, is β = Jh/ Je ∼ 3 - 4.5. Attempts at calculating β for these LEDs have shown that the effects of high level injection, built-in field and breakdown of the depletion approximation must be taken into account if realistic device modelling is to be carried out. The results of this work are believed to have important practical implications because they suggest that significant improvements in device efficiencies can be obtained by modifying the doping profile to increase the electron injection efficiency into the higher luminescence efficiency p-type material.
- Publication:
-
Solid State Electronics
- Pub Date:
- June 1980
- DOI:
- 10.1016/0038-1101(80)90044-1
- Bibcode:
- 1980SSEle..23..611T
- Keywords:
-
- Electroluminescence;
- Energy Conversion Efficiency;
- Gallium Phosphides;
- Light Emitting Diodes;
- P-N Junctions;
- Volt-Ampere Characteristics;
- Carrier Injection;
- Decay Rates;
- Epitaxy;
- Molecular Diffusion;
- Time Dependence;
- Electronics and Electrical Engineering