Charge Carrier Characteristics of Doped Semiconductor Heterostructures

Nate Johnson


A Dimension 3100 scanning probe microscope was modified for use in ballistic electron emission microscopy (BEEM). BEEM is a type of scanning tunneling microscopy that adds a third electrical contact in order to study electrical conduction in buried interfaces of multi-layered systems. BEEM was used in order to study the properties of majority carriers traveling across meta-semiconductor interfaces in different types of semiconductor heterostructures. Samples of Au deposited on n-GaAs and Ni deposited on n-GaN nanowire were examined. BEEM was used to measure the Schottky barrier height of AU-GaAs samples by collecting data on the current flowing from the buried GaAs layer as forward bias is applied to the sample. The Schottky barrier height for Au-GaAs was successfully measured for some samples at Vbc = 0.95±0.007 V, which matches well with previous experimental results. The second conductions band minimum was also detected at VL = 1.26±0.11 V, also in agreement with other studies. Preliminary data on Ni-GaN nanowire systems were collected. The close agreement between results obtained for Au-GaAs samples and other studies means that the experimental apparatus can reasonably detect current in buried interfaces accurately.