The most closely related prior III-V semiconductor lasers are based, variously, on strained InGaAs quantum wells and InAs quantum dots on InP substrates. The emission wavelengths of these prior devices are limited to about 2.1 µm because of critical quantum-well thickness limitations for these lattice-mismatched material systems.

In the Proposed Semiconductor Laser, the active region would contain In(As)Sb quantum dots, which emit at wavelengths from 1.7 to 2.3 μm. The first-order grating would be included, optionally, to select operation at a single wavelength
The major obstacle to realizing the proposed laser is the difficulty of fabricating InSb quantum dots in sufficient density on an InP substrate. This difficulty arises partly because of the weakness of the bond between In and Sb and partly because of the high temperature needed to crack metalorganic precursor compounds during the vapor-phase epitaxy used to grow quantum dots: The mobility of the weakly bound In at the high growth temperature is so high that In adatoms migrate easily on the growth surface, resulting in the formation of large InSb islands at a density, usually less than 5 × 109 cm-2, that is too low for laser operation.

The mobility of the In adatoms could be reduced by introducing As atoms to the growth surface because the In-As bond is about 30 percent stronger than is the In-Sb bond. The fabrication of the proposed laser would include a recently demonstrated process that involves the use of alternative supplies of precursors to separate group-III and group-V species to establish local non-equilibrium process conditions, so that In(As)Sb quantum dots assemble themselves on a (001) InP substrate at a density as high as 4×1010 cm-2. Room-temperature photoluminescence spectra of quantum dots formed by this process indicate that they emit at wavelengths from 1.7 to 2.3 µm.

This work was done by Yueming Qiu of Caltech for NASA’s Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at under the Physical Sciences category.

In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:

Innovative Technology Assets Management


Mail Stop 202-233

4800 Oak Grove Drive

Pasadena, CA 91109-8099

(818) 354-2240

E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Refer to NPO-40653, volume and number of this NASA Tech Briefs issue, and the page number.