Photoexcited-induced sensitivity of InGaAs surface QDs to environment

Abstract

A detailed analysis of the impact of illumination on the electrical response of In 0.5 Ga 0.5 As surface nanostructures is carried out as a function of different relative humidity conditions. The importance of the surface-to-volume ratio for sensing applications is once more highlighted. From dark-to-photo conditions, the sheet resistance (SR) of a three-dimensional In 0.5 Ga 0.5 As nanostructure decays two orders of magnitude compared with that of a two-dimensional nanostructure. The electrical response is found to be vulnerable to the energy of the incident light and the external conditions. Illuminating with high energy light translates into an SR reduction of one order of magnitude under humid atmospheres, whereas it remains nearly unchanged under dry environments. Conversely, lighting with energy below the bulk energy bandgap, shows a negligible effect on the electrical properties regardless the local moisture. Both illumination and humidity are therefore needed for sensing. Photoexcited carriers can only contribute to conductivity if surface states are inactive due to water physisorption. The strong dependence of the electrical response on the environment makes these nanostructures very suitable for the development of highly sensitive and efficient sensing devices.

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.…”

Scanning tunneling spectroscopic monitoring of surface states role on water passivation of InGaAs uncapped quantum dots

“…The adsorption of water molecules onto the surface may alter the physical properties of the surface. In fact, the impact of such physisorption process on the optical and electrical properties has been recently reported, attributing the improvement to the surface passivation 7,15,[21][22][23] or oxidation 24 and therefore, to the reduction of the density of active surface states aer water adhesion. Passivation and oxidation are two processes that take place on the surface and may alter the physical properties of the surface nanostructures.…”

“…The samples were placed in an opaque and hermetically sealed box especially designed for such analysis. 15 The electrical measurements were carried out at a temperature of 24 C, under light conditions to ensure the presence of photoexcited electron-hole pairs 8 (source: blue LED, $2.7 eV, at 7.4 mW) and under different relative humidity (RH) conditions from 0% to 70%.…”

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

“…Due to the special surface sensitivity, it is expected that these SQDs should be good materials to function as humidity sensors [10,11]. Thus, a recent surge in research into the surface-sensitive performance of InGaAs SQDs has been reported [12][13][14][15].…”