AVS 52nd International Symposium
    Electronic Materials and Processing Thursday Sessions
       Session EM2-ThM

Paper EM2-ThM3
Interfacial Bond Formation in W-structured type-II IR Detectors as Revealed by Cross-Sectional Scanning Tunneling Microscopy

Thursday, November 3, 2005, 9:00 am, Room 310

Session: Heteroepitaxy and Low-Dimensional Structures
Presenter: J.C. Kim, Naval Research Laboratory
Authors: J.C. Kim, Naval Research Laboratory
J.G. Tischler, Naval Research Laboratory
I. Vurgaftman, Naval Research Laboratory
J.R. Meyer, Naval Research Laboratory
E.H. Aifer, Naval Research Laboratory
L.J. Whitman, Naval Research Laboratory
C.L. Canedy, SFA Inc.
E.M. Jackson, SFA Inc.
Correspondent: Click to Email
W-structured type-II superlattices (W-SLs) were originally developed to enhance the gain of mid-wave infrared lasers, but also have desirable properties for the design of infrared detectors. We are currently investigating ternary (and quaternary) W-SL structures composed of InAs, InGaSb (InGaAsSb), and AlInSb (AlInAsSb) layers for use in long-wave and very long-wave infrared photodiodes. Interfaces play a significant role in W-SLs because there are twice as many interfaces in each period than in a typical two-constituent SLs such as InAs/Ga(In)Sb, and therefore more options to engineer interfaces in order to compensate strain. We use x-ray diffraction to determine the overall strain in the W-SLs, and cross-sectional scanning tunneling microscopy (XSTM) to directly image the atomic-scale structure of the SLs, including the interfacial bonds, as a function of growth conditions. Differences in the local bond length of different interfaces (e.g., AlAs vs. InSb) result in specific contrast in XSTM images, making it possible to directly identify the interfacial bond types. We find that "unforced" AlSb/InAs interfaces, where both shutters are switched simultaneously with the intention of creating a neutral mix of interfacial bonds, actually consist predominantly of AlAs bonds, leading to undesirable strain. In contrast, InGaSb/InAs interfaces form as intended. We will discuss the surface science underlying the formation of these interfacial bonds, along with their effects on the optical properties and device characteristics.