Title :
ZnBeTe Buffer Layers for AlGaAs-GaAs Quantum Well Solar Cell Junctions Epitaxially Integrated on Silicon
Author :
Clark, Kevin ; Maldonado, Eduardo ; Bate, Robert T. ; Kirk, Wiley P.
Author_Institution :
NanoFAB Center, Texas Univ., Arlington, TX
Abstract :
Epitaxial growth of beryllium telluride BeTe and Zn0.06Be0.94Te by MBE on silicon was investigated as an approach towards multijunction solar cells. The good crystal properties, optical transparency, thermal stability and high p-type doping levels are positive attributes for a buffer layer for further growth of top solar cell junctions. AlGaAs-GaAs quantum well junctions were grown with close lattice matching to a Zn0.06Be0.94 Te buffer. AlGaAs layers on ZnBeTe were metastable, with thin layers roughening under growth at normal growth temperatures and rates. Planar growth was done using a low temperature growth initiation until a stable film thickness of 700 Aring. High doping of p-BeTe (2e19 /cm2) was achieved using nitrogen plasma. Electrical transport properties of p-i-n junctions under illumination were measured, integrated to silicon via an n+Si/p+Zn0.06Be0.94Te tunnel junction. One sun photocurrent was up to JSC=7.9 mA/cm2 in a 1.5 eV Al0.06Ga0.94As-GaAs junction
Keywords :
II-VI semiconductors; III-V semiconductors; aluminium compounds; beryllium compounds; buffer layers; doping profiles; electrical conductivity; gallium arsenide; molecular beam epitaxial growth; photoconductivity; semiconductor epitaxial layers; semiconductor growth; semiconductor heterojunctions; semiconductor quantum wells; silicon; solar cells; thermal stability; zinc compounds; BeTe-Si; MBE; Si; Zn0.06Be0.94Te-AlGaAs-GaAs-Si; beryllium telluride; buffer layers; crystal properties; electrical transport properties; epitaxial growth; high p-type doping levels; low temperature growth; multijunction solar cells; nitrogen plasma; optical transparency; p-i-n junctions; photocurrent; quantum well solar cell junctions; silicon; thermal stability; Buffer layers; Doping; Epitaxial growth; Optical buffering; Photovoltaic cells; Plasma measurements; Plasma temperature; Silicon; Tellurium; Zinc;
Conference_Titel :
Photovoltaic Energy Conversion, Conference Record of the 2006 IEEE 4th World Conference on
Conference_Location :
Waikoloa, HI
Print_ISBN :
1-4244-0017-1
Electronic_ISBN :
1-4244-0017-1
DOI :
10.1109/WCPEC.2006.279345
