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Title: Midgap states in a -Si:H and a -SiGe:H p - i - n solar cells and Schottky junctions by capacitance techniques

Abstract

The midgap density of states (MGDOS) in {ital a}-SiGe:H alloys is investigated by capacitance measurements on {ital p}-{ital i}-{ital n} solar cells. Past work on thick {ital a}-Si:H Schottky barriers is extended to thin {ital a}-SiGe:H {ital p}-{ital i}-{ital n} cells. Four methods of determining the MGDOS from the measured capacitance are described, and each is applied to two {ital p}-{ital i}-{ital n} devices having 0% and 62% Ge in the {ital i} layers, respectively. The first method involves fitting an equivalent circuit model to the measured admittance. Close agreement is found over a wide range of temperature and frequency. The single junction model is shown to apply equally well to {ital p}-{ital i}-{ital n} and Schottky diodes, justifying the neglect of the {ital n}-{ital i} junction and thin doped layers in the {ital p}-{ital i}-{ital n} admittance analysis. A second method determines {ital g}{sub 0} from the limiting capacitance at high temperature. The third and fourth methods extract {ital g}{sub 0} from the dependence of capacitance on voltage bias. One of these is novel, presented here for the first time. Thus, a unique feature of this study is the application of several different capacitance methods to standard {ital p}-{italmore » i}-{ital n} solar cell devices. Agreement within {plus minus}25% is found among the values of the MGDOS from the four methods. The MGDOS increases exponentially from (1--2){times}10{sup 16} to (3--4){times}10{sup 17}/cm{sup 3} eV as the Ge increases from 0% to 62%, in general agreement with results of others.« less

Authors:
 [1];  [2]
  1. Institute of Energy Conversion, University of Delaware, Newark, Delaware 19716 (United States)
  2. Institute of Energy Conversion, University of Delaware, Newark, Delaware 19716 (United States) Electrical Engineering Department, University of Delaware, Newark, Delaware 19716 (United States)
Publication Date:
OSTI Identifier:
7282210
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics; (United States)
Additional Journal Information:
Journal Volume: 71:12; Journal ID: ISSN 0021-8979
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; GERMANIUM SILICIDES; ENERGY-LEVEL DENSITY; SCHOTTKY BARRIER DIODES; SOLAR CELLS; AMORPHOUS STATE; ENERGY GAP; HYDROGEN ADDITIONS; SILICON; DIRECT ENERGY CONVERTERS; ELEMENTS; EQUIPMENT; GERMANIUM COMPOUNDS; PHOTOELECTRIC CELLS; PHOTOVOLTAIC CELLS; SEMICONDUCTOR DEVICES; SEMICONDUCTOR DIODES; SEMIMETALS; SILICIDES; SILICON COMPOUNDS; SOLAR EQUIPMENT; 140501* - Solar Energy Conversion- Photovoltaic Conversion

Citation Formats

Hegedus, S S, and Fagen, E A. Midgap states in a -Si:H and a -SiGe:H p - i - n solar cells and Schottky junctions by capacitance techniques. United States: N. p., 1992. Web. doi:10.1063/1.350444.
Hegedus, S S, & Fagen, E A. Midgap states in a -Si:H and a -SiGe:H p - i - n solar cells and Schottky junctions by capacitance techniques. United States. https://doi.org/10.1063/1.350444
Hegedus, S S, and Fagen, E A. Mon . "Midgap states in a -Si:H and a -SiGe:H p - i - n solar cells and Schottky junctions by capacitance techniques". United States. https://doi.org/10.1063/1.350444.
@article{osti_7282210,
title = {Midgap states in a -Si:H and a -SiGe:H p - i - n solar cells and Schottky junctions by capacitance techniques},
author = {Hegedus, S S and Fagen, E A},
abstractNote = {The midgap density of states (MGDOS) in {ital a}-SiGe:H alloys is investigated by capacitance measurements on {ital p}-{ital i}-{ital n} solar cells. Past work on thick {ital a}-Si:H Schottky barriers is extended to thin {ital a}-SiGe:H {ital p}-{ital i}-{ital n} cells. Four methods of determining the MGDOS from the measured capacitance are described, and each is applied to two {ital p}-{ital i}-{ital n} devices having 0% and 62% Ge in the {ital i} layers, respectively. The first method involves fitting an equivalent circuit model to the measured admittance. Close agreement is found over a wide range of temperature and frequency. The single junction model is shown to apply equally well to {ital p}-{ital i}-{ital n} and Schottky diodes, justifying the neglect of the {ital n}-{ital i} junction and thin doped layers in the {ital p}-{ital i}-{ital n} admittance analysis. A second method determines {ital g}{sub 0} from the limiting capacitance at high temperature. The third and fourth methods extract {ital g}{sub 0} from the dependence of capacitance on voltage bias. One of these is novel, presented here for the first time. Thus, a unique feature of this study is the application of several different capacitance methods to standard {ital p}-{ital i}-{ital n} solar cell devices. Agreement within {plus minus}25% is found among the values of the MGDOS from the four methods. The MGDOS increases exponentially from (1--2){times}10{sup 16} to (3--4){times}10{sup 17}/cm{sup 3} eV as the Ge increases from 0% to 62%, in general agreement with results of others.},
doi = {10.1063/1.350444},
url = {https://www.osti.gov/biblio/7282210}, journal = {Journal of Applied Physics; (United States)},
issn = {0021-8979},
number = ,
volume = 71:12,
place = {United States},
year = {1992},
month = {6}
}