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The influences of the low V/III ratio on the surface morphologies and temperature-dependent photoluminescence spectrum of InAs-GaAs quantum dots (QDs) prepared by organometallic vapor phase epitaxy are investigated. Due to the accumulation of In adatoms at the multiatomic step edge on [001] 2/sup 0/ off toward an [111] n-type GaAs substrate, InAs island growth with /spl sim/1 ML coverage takes place prior to the InAs QD formation. With increasing InAs coverage, self-assembled InAs QDs are observed near the InAs islands, which is attributed to the recapture of desorbed In atoms nucleating with supplied As atoms on the edge along [11~0]-orientation of the GaAs substrate.

The ten stacked self-assembled InAs/GaAs quantum dot infrared photodetectors (QDIP) with different Al/sub 0.3/Ga/sub 0.7/As barrier widths and growth temperatures were prepared. Asymmetric current-voltage (I-V) characteristics and 2/spl sim/7.5 /spl mu/m detection window were observed. Peak responsivity of 84 mA/W at -0.4 V and peak specific detectivity of 2.5/spl times/10/sup 9/ cm-Hz/sup 1/2//W at zero bias were observed at 50 K. The characteristics of polarization insensitivity over the incident light and the high background photocurrent suggest that the self-assembled QDIP can be operated at higher temperature (/spl sim/250 K) under normal incidence condition in contrast to quantum well infrared photodetector (QWIP).

In this letter, a 256/spl times/256 midwavelength infrared focal plane array (FPA) based on 30-period InAs-GaAs quantum-dot infrared photodetectors (QDIPs) is fabricated. The demonstrated original real-time nonuniformity corrected thermal images of hot soldering iron head with 30-Hz frame rate for the FPA are observed. Without additional light-coupling scheme, the QDIP FPA module is first operated at temperatures higher than 135 K under normal-incident condition with a 30/spl deg/ field of view and f/2 optics. For single device performances, a similar QDIP device with a 30-period InAs-GaAs QD structure is fabricated under the same processing procedure. High specific detectivity D/sup */ 1.5/spl times/10/sup 10/ cm/spl middot/Hz/sup 1/2//W and low noise current density 5.3/spl times/10/sup -13/ A/Hz/sup 1/2/ at applied voltage 0.3 V are observed.

An unpassivated InAs p-i-n photodetector with excellent performance at room temperature was demonstrated. The zero-bias resistance area products of the diode with 720-nm thick i-layer are 8.1 /spl Omega/-cm/sup 2/ at room temperature and as high as 1.3 M /spl Omega/-cm/sup 2/ at 77 K. At 77 K, the diode exhibits a breakdown voltage exceeding 13 V. When tested under a 500 K blackbody source, the measured detectivity limited by Johnson noise is 1.2/spl times/10/sup 10/ cm-Hz/sup 1/2 //W at room temperature and 8.1/spl times/10/sup 11/ cm-Hz/sup 1/2 //W at 77 K. To our knowledge, this is the best data for a room temperature infrared detector.