Unintentional As incorporation in molecular beam epitaxially grown InAs/AlSb/GaSb heterostructures

We investigate unintentional arsenic incorporation during the molecular-beam epitaxial growth of AlSb/InAs/GaSb heterostructures, using both a standard As sub4 evaporation cell and a valved arsenic cracker. When a standard As, cell is used, unintentional arsenic concentrations as large as 10-20 % can be incorporated into the AlSb and GaSb layers from the background As ambient in the growth chamber, both during growth and on stationary surfaces. This incorporation can be controlled and suppressed with the use of a valved As cracker. Suppression of the As background substantially improves the electrical transport properties of AlSb/InAs/AlSb quantum well structures.