TECHNIQUE TO CHARACTERIZE THE INTERFACES PRESENT IN SEMICONDUCTOR SUPERLATTICES

THE ELECTRONIC AND OPTICAL PROPERTIES OF DEVICES BASED ON SEMICONDUCTOR SUPERLATTICES ARE FOUND TO BE SENSITIVE TO THE ATOMIC ARRANGEMENT AT OR NEAR THE INTERFACE OF THE COMPOSITIONAL MODULATION. THE EXAMINATION OF THE MATERIAL STATE OF THESE INTERFACES IS THEREFORE AN ESSENTIAL TASK. WE PROPOSE TO APPLY TRANSMISSION ELECTRON MICROSCOPY (TEM) TO THIS PROBLEM. WITH THIS TECHNIQUE, IT IS POSSIBLE TO STUDY THE NATURE OF THE DEFECTS PRESENT AT THE INTERFACE. IN ADDITION, THE ELECTRON MICROSCOPE CAN BE OPERATED UNDER A HIGH RESOLUTION SCALE WHEREBY PHASE CONTRAST MICROSCOPY CAN BE USED TO STUDY INTERFACE ON A MICROSCOPIC SCALE (APPROX 3A). AN ESSENTIAL PART OF ANY ELECTRON MICROSCOPIC STUDY IS THE PREPARATION OF THIN SPECIMENS. IN PHASE I ACTIVITIES WILL BE DIRECTED AT DEVELOPING TECHNIQUES FOR MAKING TWO DIFFERENT TYPES OF SPECIMEN, NAMELY (A) PLAN VIEW AND (B) CROSS(X)SECTIONAL VIEW SAMPLES. IN THE PLAN VIEW CASE IT IS POSSIBLE TO SEE THE CHARACTERISTICS OF THE TOP LAYER OF A DEVICE, WHEREAS WITH THE X-SECTIONAL TECHNIQUES IT WOULD BE POSSIBLE TO SEE THE INTERFACE DIRECTLY. ATTEMPTS WILL BE MADE IN PHASE I TO STUDY INTERFACES WITH HIGH RESOLUTION PHASE CONTRAST ELECTRON MICROSCOPY. THE MATERIAL CHARACTERISTICS OF INTERFACE CAN THEN BE RELATED TO THE ELECTRONIC AND OPTICAL PROPERTIES OF DEVICES.