Comparison of various GaSb-based device structures for application in thermophotovoltaic cells
|Krystyna Golaszewska 1, Tadeusz T. Piotrowski 1, Jaroslaw Rutkowski 2, Ewa Papis 1, Renata Kruszka 1, Elzbieta Dynowska 3, Jacek Ratajczak 1, Anna Piotrowska 1|
1. Institute of Electron Technology (ITE), al. Lotników 32/46, Warszawa 02-668, Poland
InGaAsSb compounds lattice-matched to GaSb substrate could potentially be used in a variety of optoelectronic devices operating in mid-infrared domain. Recently, thermophotovoltaic devices (TPV) based on InGaAsSb active layer attract increased attention. In this context, the optimisation of InGaAsSb/AlGaAsSb structures is of special concern.
The aim of this work is the optimisation of the designs to create the best structure for GaSb-based TPV cells, specifically with respect to comparison between p-n InGaAsSb homojunctions vs. p-n InGaAsSb/AlGaAsSb heterojunctions, and p-on-n vs. n-on-p cell configurations.
InGaAsSb/AlGaAsSb structures were grown by liquid phase epitaxy (LPE) technique in horizontal sliding boat system with Pd-diffused hydrogen atmosphere. The substrates for LPE growth were n- and p-type GaSb wafers, with the concentration of n ~ 4·1017 cm-3 and p ~ 5·1018 cm-3, respectively. 6N Ga, In, Sb and undoped GaAs were used as source materials and 6N Te as a dopant. The processes were performed at temperatures To ~ 530oC and To ~ 593oC, at the cooling rate R = 0.5oC/min. The post-growth characterisation included morphological and compositional analysis using AFM, TEM, EPXMA, and SIMS as well as transport measurement using van der Pauw and C-V methods.
The mesa-type devices with mesa size of 1mm´1mm were formed using photolithography and reactive ion etching in BCl3 plasma. AgTe/Cr/Au and Au/Zn/Au metallizations were applied for backside n-type and front p-type ohmic contacts, respectively. The photodiode performance was established by measurements of the current-voltage characteristics, quantum efficiency, and spectral responsivity at 300 K. The relative photoresponse spectra were measured with a transimpedance amplifier coupled to a Fourier transform infrared (FTIR) spectrometer.
The most promising results have been obtained with 3-layer n-GaSb/n-GaInAsSb/p-GaAlAsSb heterostructure grown on n-GaSb substrate, characterized by quantum efficiency η = 0,55 and responsivity RI = 0,85 A/W @ λ = 2,0 µm.
Part of the research was supported by the grant no. 3 T11B 00926 from the Ministry of Education and Science.
Presentation: Poster at Joint Fith International Conference on Solid State Crystals & Eighth Polish Conference on Crystal Growth, by Krystyna Golaszewska
See On-line Journal of Joint Fith International Conference on Solid State Crystals & Eighth Polish Conference on Crystal Growth
Submitted: 2007-01-15 19:40 Revised: 2009-06-07 00:44