Engineering topics

Andersson, P. O.

Publications and source records attributed to Andersson, P. O..

3 records

NASA NTRS1989

Optically addressed spatial light modulators by MBE-grown nipi MQW structures

Promising approaches for achieving optically addressed spatial light modulators (O-SLMs) are investigated based on combining nipi and multiple quantum well structures. Theoretical aspects of photooptic effects achievable in such structures are treated. Test structures are grown by molecular beam epitaxy using two material systems. (In,Ga)As/GaAs and (Al,Ga)As/GaAs. Experiments show large optically controlled modulation of the absorption coefficient in the quantum well layers, a log power dependence on the control signal, millisecond and shorter time response, and generally predictable behavior. The results are encouraging for several different O-SLM device structures proposed.

Maserjian, Joseph↗

NASA NTRS1989

Optically controlled absorption modulator based on state filling of In(x)Ga(1-x)As/GaAs quantum wells

The first demonstration of an optically controlled absorption modulator based on state filling in a periodically doped In(x)Ga(1-x)As/GaAs multiple quantum well structure is reported. Differential absorption of approximately 10,000/cm is observed in the quantum wells of the test structure at saturation pump powers. Photoluminescence and time-resolved modulation measurements confirm the predicted behavior of carrier recombination and give a measure of enhanced carrier lifetime of approximately 1 ms. These initial results show the potential for developing these structures into optically addressed spatial light modulators.

Iannelli, J. M.↗

NASA NTRS1988

Increased effective barrier heights in Schottky diodes by molecular-beam epitaxy of CoSi2 and Ga-doped Si on Si(111)

Increasing the effective Schottky-barrier height of epitaxial CoSi2/Si(111) diodes by the use of thin, highly doped Si layers in close proximity to the metal-semiconductor interface has been studied. Intrinsic Si, Si doped by coevaporation of Ga, and epitaxial CoSi2 layers have all been grown in the same molecular-beam epitaxy system. Current-voltage and photoresponse characterization yield barrier heights ranging from 0.61 eV for a sample with no p(+) layer to 0.89 eV for a sample with a 20-nm-thick p(+) layer. These results are compared to theoretical values based on a one-dimensional solution of Poisson's equation under the depletion approximation.

Fathauer, R. W.↗