We report a high detectivity of 3×1011 cm Hz1/2/W at 78 K for normal-incidence quantum dot infrared photodetectors with ten layers of undoped InAs/InGaAs/GaAs quantum dot active regions. The high detectivity seen at 1.4 V corresponds to photoresponse peaks at 9.3 and 8.7 μm for positive and negative bias, respectively.

We have performed a comprehensive investigation of n-type quantum dot infrared photodetectors (QDIPs) based on InAs/GaAs epitaxical island quantum dots (QDs) grown via the innovative punctuated island growth technique. The structural properties of the QDs were investigated with cross-sectional transmission electron microscopy and atomic force microscopy. The electronic properties of the QDs inserted in QDIP devices were investigated with photoluminescence (PL), PL excitation, and intra- and inter-band photocurrent spectroscopy. The influence of AlGaAs layers inserted into the QDIP active regions on the performance of dark current and inter- and intra-band photocurrent was examined. Initial results on intra-band responsivity and detectivity of these QDIPs at 77 K with undoped active region show promise for application.

We report InAs quantum dot infrared photodetectors that utilize In0.15Ga0.85As strain-relief cap layers. These devices exhibited normal-incidence photoresponse peaks at 8.3 or 8.8 μm for negative or positive bias, respectively. At 77 K and −0.2 V bias the responsivity was 22 mA/W and the peak detectivity D* was 3.2×109 cm Hz1/2/W.

We report the realization of electron intraband absorption based middle- (∼5.6 μm) and long- (∼10 μm) wavelength infrared (IR) photoresponse for normally incident radiation on InGaAs-capped GaAs(001)/InAs quantum dots(QDs) in a n–i( QD )–n structure. The relative photoresponse in this dual-wavelength structure is tunable up to two orders of magnitude with bias. The full width at half maximum of the long-wavelength IR intraband photocurrent peak at 80 K is as narrow as 8.2 meV.

We report noise characteristics, carrier capture probability, and photoconductive gain of InAs quantum-dot infrared photodetectors with unintentionally doped active regions. At 77 K, a photoconductive gain of 750 was observed at a bias of 0.7 V. The high gain is a result of the low carrier capture probability: $\text{p=0.0012.}$