Hot-carrier separation in heterostructure nanowires observed by electron-beam induced current

Abstract

The separation of hot carriers in semiconductors is of interest for applications such as thermovoltaic photodetection and third-generation photovoltaics. Semiconductor nanowires offer several potential advantages for effective hot-carrier separation such as: a high degree of control and flexibility in heterostructure-based band engineering, increased hot-carrier temperatures compared to bulk, and a geometry well suited for local control of light absorption. Indeed, InAs nanowires with a short InP energy barrier have been observed to produce electric power under global illumination, with an open-circuit voltage exceeding the Shockley-Queisser limit. To understand this behaviour in more detail, it is necessary to establish control over the precise location of electron-hole pair-generation in the nanowire. In this work we perform electron-beam induced current measurements with high spatial resolution, and demonstrate the role of the InP barrier in extracting energetic electrons.We interprete the results in terms of hot-carrier separation, and extract estimates of the hot carriers’ mean free path.

Hot-carrier optoelectronic devices based on semiconductor nanowires

“…These observations matches well with the mechanism for photocurrent generation described earlier (Fig. 10(a)) and the carrier separation observed 161 by EBIC in Fig. 10(b).…”

“…10(c), an effective hot-carrier relaxation length on the order of 100 nm was extracted. 161 Similar numbers have been found with the help of EBIC for holes in InSb/InAs nanowires. 162 Not yet published data of Kumar et al 136 observed ballistic transport of 0.5 eV electrons over a distance on the order of 200-260nm in InAs nanowires.…”

“…10(c)). 161 The EBIC data demonstrates that carrier excitation close to the barrier is required for current generation, likely in order to prevent carrier relaxation before the electrons reach the barrier. This is the author's peer reviewed, accepted manuscript.…”

Theory of non-equilibrium ‘hot’ carriers in direct band-gap semiconductors under continuous illumination

“…Despite the extensive work on the topic, most studies involved only a macroscopic description of the problem, while the fewer existing state-of-the-art modelling of the NESS have several limitations. First, the tenet that the photo-excited HCs ultimately achieve the lattice temperature in the steady-state [31] has been challenged in a recent experiment on group III-V semiconductors; it unveils that in the NESS carrier temperatures can be much higher than lattice temperature [32][33][34][35]. A theoretical understanding of the existence of such a high carrier-temperature in NESS is still lacking [32][33][34][35], especially in light of the different techniques available for measuring the various temperatures.…”

Scanning probe-induced thermoelectrics in a quantum point contact

“…Subsequently, this possibility of measuring local temperature on the nanoscale was leveraged to image the Peltier effect in graphene nanoconstrictions 3 and nanowire heterostructures. 4 Spatially-resolved images of the Seebeck effect were measured as well by engineering local heaters with scanning tunneling 5 or thermal 3,4 microscopes, focused laser 6 or electron 7 beams, or Joule-heated nanowires. 8 Contrary to conventional (longitudinal) thermoelectric measurements that are performed across two terminals, such experiments involve a third terminal (e.g.…”