Interface study on heterostructured GaP–GaAs nanowires

Abstract

The interface chemical composition of heterostructured GaP-GaAs nanowire segments was studied by the use of energy-dispersive x-ray analysis. An arsenic-rich tail in the GaP segments following GaAs could be minimized by reducing the AsH(3) molar fraction and the growth rate. For the temperature regime used for vapour-liquid-solid growth, we observe the opposite trend on interface sharpness compared to high-temperature layer-by-layer growth, that is, the sharpness of the interface improves with reducing temperature.

Transition region width of nanowire hetero- and pn-junctions grown using vapor–liquid–solid processes

“…Therefore the Si vapor source still had a normalized strength 1, and the total vapor strength was 1.1. However, as long as α is small which was satisfied in the experiment, (8) and (9) can closely approximate the results.…”

“…First, (8) and (9) are used to fit an experimentally measured concentration profile of a Si-Ge junction, and second, (10) is used to fit a set of junction abruptness data, all due to Clark et al [5]. The calculated and experimental results of the Si-Ge concentration profile are shown together in Fig.…”

“…Here for simplicity we assumed that the droplet is a hemisphere and hence α = 1. Although quantitative data are not available, it is known that the transition regions of some III-V heterojunctions [1,8,9] can be much sharper than those of Si-Ge [4,5]. This is the case because the solubilities of the group V elements are small in Au, while the solubilities of the group IV elements Si and Ge are both over 20 at.…”

“…Thus, extensive studies have been performed on the preparation, property, and growth kinetics of nanowires and nanowire structures with either hetero-or pn-junctions [1][2][3][4][5][6][7][8][9]. Nanowire heterojunction structures of various semiconductors have been fabricated, e.g., Si-Ge [3][4][5], GaAs-InAs [6] and GaP-GaAs [7,8].…”

“…We believe that this process is the very basic reason why the experimentally grown heterojunctions all possess graded transition regions with large junction widths, instead of abrupt ones with atomic scale junction widths. Although in theory it is impossible to grow atomic scale abrupt heterojunctions, it has been reported that some III-V compound semiconductor heterojunctions can be fairly sharp [1,8,9], while much wider junctions were always obtained for the Si-Ge cases. In a recent experiment, it has also been found that the width of the Si-Ge heterojunctions is directly proportional to the nanowire size [5].…”