AL(AS,SB) HETEROBARRIERS ON INAS - GROWTH, STRUCTURAL-PROPERTIES AND ELECTRICAL-TRANSPORT

We discuss structural and electrical properties of AlAsxSb1-x bulk lay ers and InAs/AlAsxSb1-x heterostructures grown by molecular beam epita xy over a wide range of composition (0 less than or equal to x less th an or equal to 0.4). We demonstrate the strong sensitivity of the stru ctural quality and the composition of Al(As,Sb) on growth parameters s uch as substrate temperature. As:Sb Bur ratio. as well as total group- V Hus, and discuss the influence oi a miscibility gap on the molecular beam epitaxial growth of Al(As,Sb). We also find that both the compos ition and the growth temperature strongly influence the surface morpho logy: Al(As,Sb)-especially when grown at low substrate temperature - a ppears to grow in an island-coalescence mode rather than in a two-dime nsional manner as it does for pure AlAs or AlSb. The electrical transp ort along AlSb/InAs/Al(As,Sb) quantum wells is strongly influenced by tile growth temperature of Al(As,Sb) and we observe the formation of a dditional defects when the top barrier was grown at low substrate temp erature. The transport across InAs/Al(As,Sb) heterojunctions was found to depend on both the growth temperature and the arsenic composition. An increase in arsenic composition results in a strongly decreased cu rrent across the heterojunction. From ballistic electron emission spec troscopy experiments. we confirm the transition from a staggered band lineup for InAs-AlSb to a straddled band lineup For InAs/AlAsxSb1-x fo r x = 0.16. (C) 1998 Published by Elsevier Science B.V. All rights res erved.