Increased Optoelectronic Quality and Uniformity of Hydrogenated p-InP Thin Films

Abstract

ABSTRACT:The thin-film vapor-liquid-solid (TF-VLS) growth technique presents a promising route for high quality, scalable and cost-effective InP thin films for optoelectronic devices. Towards this goal, careful optimization of material properties and device performance is of utmost interest. Here, we show that exposure of polycrystalline Zn-doped TF-VLS InP to a hydrogen plasma (in the following referred to as hydrogenation) results in improved optoelectronic quality as well as lateral optoelectronic uniformity. A combination of low temperature photoluminescence and transient photocurrent spectroscopy were used to analyze the energy position and relative density of defect states before and after hydrogenation. Notably, hydrogenation reduces the relative intra-gap defect density by one order of magnitude. As a metric to monitor lateral optoelectronic uniformity of polycrystalline TF-VLS InP, photoluminescence and electron beam induced current mapping reveal homogenization of the grain versus grain boundary upon hydrogenation. At the device level, we measured more than 260 TF-VLS InP solar cells before and after hydrogenation to verify the improved optoelectronic properties. Hydrogenation increased the average open-circuit voltage (V OC ) of individual TF-VLS InP solar cells by up to 130 mV, and reduced the variance in V OC for the analyzed devices.

Low‐Dimensional Metal Halide Perovskite Photodetectors

“…Electrically active intrinsic point defects, which lead to unintentional mid‐gap defect states including interstitials and vacancies with shallow energy levels, are detrimental to the optoelectronic device performance. [ 20 ] Therefore, investigations on 2D MHPs with low defect density were reported. PDs based on (PEA) 2 PbI 4 ·(CH 3 NH 3 PbI 3 ) n −1 with low defect density can achieve high D * of 10 13 Jones due to lower defect levels compared with 3D perovskites.…”

“…Electrically active ions or other impurities might segregate along grain boundaries, causing nonuniform electrical properties over the films. [ 20 ] Moreover, it is revealed that the grain boundaries in polycrystalline MHPs are especially unstable and highly vulnerable to moisture. [ 21 ] These effects hinder their practical applications in stable functional devices.…”

Band Tailing and Deep Defect States in CH3NH3Pb(I1–xBrx)3 Perovskites As Revealed by Sub-Bandgap Photocurrent

“…12,13 For CH 3 residing deep in the gap are rarely observed. In this regard, highly sensitive sub-bandgap EQE is a particularly powerful approach because it is capable of probing ultra-low photocurrents due to sub-bandgap absorption that can be several orders of magnitude weaker than absorption at E g .…”

Low-Cost Approaches to III–V Semiconductor Growth for Photovoltaic Applications

“…Work is currently underway on the use of a halide transport agent to overcome these hurdles. Similar difficulties controlling dopant distribution are likely in TF-VLS growth as dopants percolate to grain edges (where diffusion rates are typically much higher) in the final device …”

“…This provided final N A = 1.9 × 10 17 cm –3 and enabled InP photocathodes for PEC water splitting . Later work showed that treatment of the film postdoping with hydrogen plasma increased the optoelectronic quality and uniformity of the doped material by forming neutral complexes with Zn …”