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Hydrogen passivation of n+p and p+n heteroepitaxial InP solar cell structuresHigh-efficiency, heteroepitaxial (HE) InP solar cells, grown on GaAs, Si or Ge substrates, are desirable for their mechanically strong, light-weight and radiation-hard properties. However, dislocations, caused by lattice mismatch, currently limit the performance of the HE cells. This occurs through shunting paths across the active photovoltaic junction and by the formation of deep levels. In previous work we have demonstrated that plasma hydrogenation is an effective and stable means to passivate the electrical activity of dislocations in specially designed HE InP test structures. In this work, we present the first report of successful hydrogen passivation in actual InP cell structures grown on GaAs substrates by metalorganic chemical vapor deposition (MOCVD). We have found that a 2 hour exposure to a 13.56 MHz hydrogen plasma at 275 C reduces the deep level concentration in HE n+n InP cell structures from as-grown values of approximately 10(exp 15)/cm(exp -3), down to 1-2 x 10(exp 13)/cm(exp -3). The deep levels in the p-type base region of the cell structure match those of our earlier p-type test structures, which were attributed to dislocations or related point defect complexes. All dopants were successfully reactivated by a 400 C, 5 minute anneal with no detectable activation of deep levels. I-V analysis indicated a subsequent approximately 10 fold decrease in reverse leakage current at -1 volt reverse bias, and no change in the forward biased series resistance of the cell structure which indicates complete reactivation of the n+ emitter. Furthermore, electrochemical C-V profiling indicates greatly enhanced passivation depth, and hence hydrogen diffusion, for heteroepitaxial structures when compared with identically processed homoepitaxial n+p InP structures. An analysis of hydrogen diffusion in dislocated InP will be discussed, along with comparisons of passivation effectiveness for n+p versus p+n heteroepitaxial cell configurations. Preliminary hydrogen-passivated HE InP cell results will also be presented.
Document ID
19960007891
Document Type
Conference Paper
Authors
Chatterjee, B. (Ohio State Univ. Columbus, OH, United States)
Ringel, S. A. (Ohio State Univ. Columbus, OH, United States)
Hoffman, R., Jr. (Essential Research, Inc. Cleveland, OH., United States)
Date Acquired
September 6, 2013
Publication Date
October 1, 1995
Publication Information
Publication: NASA. Lewis Research Center, Proceedings of the 14th Space Photovoltaic Research and Technology Conference (SPRAT 14)
Subject Category
ENERGY PRODUCTION AND CONVERSION
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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IDRelationTitle19960007876Analytic PrimaryProceedings of the 14Th Space Photovoltaic Research and Technology Conference (SPRAT 14)