Direct Determination of Minority Carrier Diffusion Lengths at Axial GaAs Nanowire p鈥搉 Junctions
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- 作者：Christoph Gutsche ; Raphael Niepelt ; Martin Gnauck ; Andrey Lysov ; Werner Prost ; Carsten Ronning ; Franz-Josef Tegude
- 刊名：Nano Letters
- 出版年：2012
- 出版时间：March 14, 2012
- 年：2012
- 卷：12
- 期：3
- 页码：1453-1458
- 全文大小：382K
- 年卷期：v.12,no.3(March 14, 2012)
- ISSN：1530-6992
文摘
Axial GaAs nanowire p鈥搉 diodes, possibly one of the core elements of future nanowire solar cells and light emitters, were grown via the Au-assisted vapor鈥搇iquid鈥搒olid mode, contacted by electron beam lithography, and investigated using electron beam induced current measurements. The minority carrier diffusion lengths and dynamics of both, electrons and holes, were determined directly at the vicinity of the p鈥搉 junction. The generated photocurrent shows an exponential decay on both sides of the junction and the extracted diffusion lengths are about 1 order of magnitude lower compared to bulk material due to surface recombination. Moreover, the observed strong diameter-dependence is well in line with the surface-to-volume ratio of semiconductor nanowires. Estimating the surface recombination velocities clearly indicates a nonabrupt p鈥搉 junction, which is in essential agreement with the model of delayed dopant incorporation in the Au-assisted vapor鈥搇iquid鈥搒olid mechanism. Surface passivation using ammonium sulfide effectively reduces the surface recombination and thus leads to higher minority carrier diffusion lengths.