Strong Influence of the Humidity on the Electrical Properties of InGaAs Surface Quantum Dots

Abstract

The impact of the environment on the electrical properties of uncapped In0.5Ga0.5As nanostructures is studied as a function of different atmospheres for sensing applications. Electrical response from surface quantum dots (QD) shows a strong dependence on the atmosphere, in contrast to the response of 2D nanostructures. The sheet resistance drops by 99% from vacuum to air, and decreases more than one order of magnitude when relative humidity changes from 0 to 70%. The adsorption of water molecules onto the QD surface improves the conductivity likely by reducing the density of surface states acting as carrier traps, which enhances electron transport.

Strong Influence of Temperature and Vacuum on the Photoluminescence of In0.3Ga0.7As Buried and Surface Quantum Dots

“…In turn, more electrons become available for the radiative recombination, which results in an increase in the overall PL intensity. The enhancements of SQDs PL intensity by the polar molecules have also been reported by other research groups [20][21][22]. Conversely, there are no obvious varieties in the BQDs PL spectra as the vacuum decreases, as shown in Fig.…”

Photoexcited-induced sensitivity of InGaAs surface QDs to environment

“…Device-heating effects during illumination are discarded due to the low powers used. I-V characteristics were measured under a constant incident blue-light power and by varying the relative humidity into the cavity from dry (0% RH) to 60% (saturated region: it was previously reported that above 50% of RH, but SR does not exhibit any further reduction [13]). Such a sequence was repeated for several LED powers: at 0 (darkness), 1.6, 4.0, 7.4, 11.0 and 12.4 μW.…”

“…SR as a function of the applied bias was previously found to present a symmetrical response [13]. Thus, as a representative value, in this study we focus on the reverse bias region in order to perform a narrower analysis.…”

“…Materials such as porous Si [3], ZnO nanostructures [4], colloidal II-VI quantum dots (QDs), graphene [5], carbon QDs [6] and III-V semiconductors [7][8][9] have been proposed as candidates for the development of environmental sensing devices. In particular, surface compound nanostructures based on the high mature arsenide technology (III-As) have recently reported a high sensitivity to external conditions [10][11][12][13]. The strong correlation between external conditions and the optical properties of the InGaAs surface QD (SQD) has been addressed to rely on the coupling between surface and confined states [14][15][16][17].…”

“…Recent studies have shown the strong impact of the relative humidity (RH) in the atmosphere on the SR [13], i.e. the conductivity increases in high RH environments.…”