Gas Sensitivity of In0.3Ga0.7As Surface QDs Coupled to Multilayer Buried QDs

Abstract

A detailed analysis of the electrical response of In0.3Ga0.7As surface quantum dots (SQDs) coupled to 5-layer buried quantum dots (BQDs) is carried out as a function of ethanol and acetone concentration while temperature-dependent photoluminescence (PL) spectra are also analyzed. The coupling structure is grown by solid source molecular beam epitaxy. Carrier transport from BQDs to SQDs is confirmed by the temperature-dependent PL spectra. The importance of the surface states for the sensing application is once more highlighted. The results show that not only the exposure to the target gas but also the illumination affect the electrical response of the coupling sample strongly. In the ethanol atmosphere and under the illumination, the sheet resistance of the coupling structure decays by 50% while it remains nearly constant for the reference structure with only the 5-layer BQDs but not the SQDs. The strong dependence of the electrical response on the gas concentration makes SQDs very suitable for the development of integrated micrometer-sized gas sensor devices.

Carrier Injection to In0.4Ga0.6As/GaAs Surface Quantum Dots in Coupled Hybrid Nanostructures

“…High-density surface states provide surface sensitivity for InGaAs SQDs being used as sensor applications. However, these surface states are also centers for non-radiative recombination and ultimately result in the trapping of carriers at the surface [16,17]. In order for SQD sensors to have stronger optical and electrical responsivity, hybrid structures are generally introduced, where, for example, stacking layers of QDs are embedded under a thin spacer below the SQDs [16][17][18][19].…”

“…However, these surface states are also centers for non-radiative recombination and ultimately result in the trapping of carriers at the surface [16,17]. In order for SQD sensors to have stronger optical and electrical responsivity, hybrid structures are generally introduced, where, for example, stacking layers of QDs are embedded under a thin spacer below the SQDs [16][17][18][19]. In these multi-layered structures, the buried QDs (BQDs) act as carrier reservoirs, supplying additional carriers to the SQDs and tuning the performances of the SQDs.…”