Role of Dislocation in InGaN/GaN Quantum Wells Grown on Bulk GaN and Sapphire Substrates

Tomoya SUGAHARA  Shiro SAKAI  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E83-C   No.4   pp.598-604
Publication Date: 2000/04/25
Online ISSN: 
DOI: 
Print ISSN: 0916-8516
Type of Manuscript: INVITED PAPER (Special Issue on Blue Laser Diodes and Related Devices/Technologies)
Category: 
Keyword: 
dislocation,  homoepitaxy,  heteroepitaxy,  nonradiative recombination center,  phase separation,  band-tail states,  

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Summary: 
Dislocation properties in InGaN/GaN Quantum Wells and GaN grown on bulk GaN and sapphire substrates by metalorganic chemical vapor deposition (MOCVD) were characterized using cathodoluminescnece (CL), transmission electron microscopy (TEM), atomic force microscopy (AFM) and photoluminescence (PL). It was clearly demonstrated that dislocations act as nonradiative recombination centers in both n-type (undoped and Si-doped) GaN and InGaN layers. Furthermore the very short-minority carrier diffusion length was a key parameter to explain the high light emission efficiency in GaN-based light emitting diodes (LEDs) prepared on sapphire substrates. On the other side band-tail states were detected in the heteroepitaxial InGaN layers only by temperature dependence PL measurement. Additionally InGaN phase separation, which consists of few micron domains, has been produced under growth conditions which favors the spiral growth. These results indicate that the dislocations in the InGaN layers act as triggering centers for the InGaN phase separation which cause both a compositional fluctuation and the formation of few micron phase separated domains. The homoepitaxial InGaN layers showed however quite normal behaviors for all characterizations.