We have grown GaAs quantum dots (QDs) in Al<sub>0.3</sub>Ga<sub>0.7</sub>As matrix by droplet epitaxy for application in single photon
sources. This growth method enables the formation of QDs without strain, with emission wavelengths of around 700 nm
within the optimal detection range of cost effective silicon detector, and with reduced surface density of several tens to a
few QDs per μm<sup>2</sup> for easier isolation of single QDs. The optical properties of QDs were envisaged by exciton and
biexciton emission peaks identified from power dependent and time-resolved micro-photoluminescence (μ-PL)
measurements. The possibility of fabricating photonic crystal (PC) resonator including a single QD was shown by
obtaining precise spectral and spatial information from a few QDs in a mesa structure, utilizing cathodoluminescence
We have investigated the device characteristics of quantum dot infrared photo detector (QDIP) utilizing InAs QDs in an In<sub>0.15</sub>Ga<sub>0.85</sub>As quantum well structure. Device characteristics, such as dark current, photoluminescence (PL), and photocurrent spectra, have been measured. Two peak positions were measured at 163 and 219 meV in photocurrent spectrum. The photo-current of the peak at 163 meV was larger than that at 219 meV. The full width at half maximum (FWHM) of the peak at 163 meV was 18 meV, which was attributed to bound-to-bound transition. In<sub>0.15</sub>Ga<sub>0.85</sub>As layers were believed to contribute to induce bound-to-bound transition energy (163 meV). The activation energies of electrons in an InGaAs QDs were determined to be 171 meV and 221 meV from temperature-dependent integrated PL intensities. These activation energies from PL measurement are quite well matched to peak IR detection energies of 163 meV and 219 meV from the photo-current spectrum. This result implies that one can estimate the peak IR detection wavelength of QDIP from PL measurements of QDIP structure before its fabrication and measurement.