We demonstrate the dimensional tuning of InAs self-assembled quantum dots ͑QDs͒ by changing the growth kinetics during the capping of InAs islands with GaAs. Modifying the growth sequence during the capping of InAs islands, allows us to tune the thickness and lateral dimensions of the QDs while keeping the wetting layer thickness constant. Using the same method but embedding the tuned InAs islands into AlAs layers allows to further blueshift the photoluminescence emission to higher energies while keeping the wetting layer thickness constant. The main process responsible for the QDs size modification is consistent with a kinetically controlled materials redistribution of the InAs islands that minimizes the energy of the epitaxial layers at the start up of the GaAs capping deposition.

We report the quantum dot infrared photodetector using the modulation doped InAs self-assembled quantum dots. By modulation doping, it is possible to remove the effect of the dopants on the energy level in InAs dots and to attribute clearly the infrared photocurrent to the carrier excitation in InAs dots. The infrared photocurrent in the detector was clearly observed up to 30 K. The peak energy and the polarization dependence of the infrared photocurrent are comparable to the infrared electron excitation from the ground state in InAs dots to the conduction band edge of GaAs barriers.

Measuring the bulk lifetime of unpassivated blocks and ingots is of great interest to the solar cell industry. The eddy‐current photoconductance method is a common choice for such measurements, employing the quasi‐steady‐state (QSS) mode for lower lifetime samples, and the transient photoconductance decay (PCD) mode for higher lifetime samples. Due to the high surface recombination velocity in unpassivated bulk samples, the lifetime measured with this method consists of components of recombination at both the surface and in the bulk. In order to determine the bulk lifetime from the measurement data, simulations of both transient and QSS mode measurements were conducted. Copyright © 2010 John Wiley & Sons, Ltd.

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High efficiency silicon solar cells demand the use of high lifetime silicon wafers. Characterization of boules and bricks before wafering allows poor quality material to be rejected before expensive processing steps. This paper extends simulation techniques previously used in quasi-steady-state-photoconductance to transient photoconductance decay measurements of high lifetime bulk samples. Simulated photogenerated carrier density profiles allow estimation of the bulk lifetime of a thick silicon sample with high surface recombination velocity.

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