Pettersson H, Trägårdh J, Persson A I, Landin L, Hessman D, Samuelson L
Center for Applied Mathematics and Physics, Halmstad University, Box 823, SE-301 18 Halmstad, Sweden.
Nano Lett. 2006 Feb;6(2):229-32. doi: 10.1021/nl052170l.
We report on spectrally resolved photocurrent measurements on single self-assembled nanowire heterostructures. The wires, typically 3 microm long with an average diameter of 85 nm, consist of InAs with a 1 microm central part of InAsP. Two different sets of wires were prepared with phosphorus contents of 15+/-3% and 35+/-3%, respectively, as determined by energy-dispersive spectroscopy measurements made in transmission electron microscopy. Ohmic contacts are fabricated to the InAs ends of the wire using e-beam lithography. The conduction band offset between the InAs and InAsP regions virtually removes the dark current through the wires at low temperature. In the optical experiments, interband excitation in the phosphorus-rich part of the wires results in a photocurrent with threshold energies of about 0.65 and 0.82 eV, respectively, in qualitative agreement with the expected band gap of the two compositions. Furthermore, a strong polarization dependence is observed with an order of magnitude larger photocurrent for light polarized parallel to the wire than for light polarized perpendicular to the wire. We believe that these wires form promising candidates as nanoscale infrared polarization-sensitive photodetectors.
我们报道了对单个自组装纳米线异质结构进行光谱分辨光电流测量的结果。这些纳米线通常长3微米，平均直径为85纳米，由InAs构成，中间有1微米长的InAsP部分。通过透射电子显微镜中的能量色散谱测量确定，制备了两组不同的纳米线，磷含量分别为15±3%和35±3%。使用电子束光刻技术在纳米线的InAs端制作欧姆接触。InAs和InAsP区域之间的导带偏移实际上消除了低温下通过纳米线的暗电流。在光学实验中，纳米线富磷部分的带间激发分别产生了阈值能量约为0.65和0.82 eV的光电流，与两种成分的预期带隙定性一致。此外，观察到强烈的偏振依赖性，平行于纳米线偏振的光产生的光电流比垂直于纳米线偏振的光大一个数量级。我们认为，这些纳米线有望成为纳米级红外偏振敏感光电探测器。
