Time-Resolved Photoinduced Thermoelectric and Transport Currents in GaAs Nanowires

Abstract

In order to clarify the temporal interplay of the different photocurrent mechanisms occurring in single GaAs nanowire based circuits, we introduce an on-chip photocurrent pump-probe spectroscopy with a picosecond time resolution. We identify photoinduced thermoelectric, displacement, and carrier lifetime limited currents as well as the transport of photogenerated holes to the electrodes. Moreover, we show that the time-resolved photocurrent spectroscopy can be used to investigate the drift velocity of photogenerated carriers in semiconducting nanowires. Hereby, our results are relevant for nanowire-based optoelectronic and photovoltaic applications.

Semiconductor nanowires studied by photocurrent spectroscopy

“…There exist two major pump-probe methods to measure the time-resolved photocurrent on a picosecond timescale. These are the photocurrent autocorrelation spectroscopy (Erhard et al 2013;Gabor et al 2012;Urich et al 2011) and the THz-time domain photocurrent spectroscopy (Erhard et al 2013;Prechtel et al 2012a).…”

“…Another possibility to measure the photocurrent of a nanowire with a picosecond timeresolution is the so-called THz time-domain photocurrent spectroscopy (Erhard et al 2013;Prechtel et al 2012a). Compared to the photocurrent autocorrelation spectroscopy, it also works in the non-saturation regime, because the time-resolution is achieved by the utilization of an Auston switch ( Figure 3).…”

“…On short timescales, in the first picoseconds after a pulsed laser excitation, the generation of additional charge carriers may cause a displacement current by which electric fields are screened. On timescales of picoseconds up to nanoseconds, the photocurrents can be dominated by the drift current of slow photogenerated charge carriers, such as holes, and the carrier life-time limited current (Erhard et al 2013;Prechtel et al 2012a). All these currents are related to electric fields within a nanowire.…”

Band structures and spatial carrier confinement in GaAs/GaP core-shell nanowires: Core/shell composition and size effects

“…This fundamentally stems from their reduced dimension which allows not only to tune electronic and optical properties but also to overcome the lattice mismatch between the NWs and silicon substrate for the compatibility with the silicon technology [4,5]. Among IIIeV semiconductor NWs, GaAs NWs are one of most investigated targets due to their medium direct band gap (~1.43 eV in bulk) [6], high carrier mobility [7], and large optical absorption, which makes them a promising candidate for the applications in field-effect transistors [8], light emitting diodes [9], single-photon sources [10], sensors, photodetectors [11], and solar cells [12].…”

Electrical contacts to single nanowires: a scalable method allowing multiple devices on a chip. Application to a single nanowire radial p-i-n junction

“…For this reason, it has been recognised that realising statistics on the devices is extremely important. Nowadays numerous contacting procedures have been adjusted to the nature of nanoscale materials and nanowires [23][24][25][26][27]. Most of them imply the contacting step of one device at a time.…”