M.Sc Thesis

M.Sc StudentShuall Nimrod
SubjectOptical and Electrical Characterization of In(Ga)As/InP
Quantum Dots Layers and IR Devices
DepartmentDepartment of Electrical and Computer Engineering
Supervisors PROFESSOR EMERITUS Gad Bahir
PROF. Dan Ritter


In this work we present the growth and analysis of self-assembled In(Ga)As Quantum Dots (QDs) in InP matrix. The QDs were grown in Stranski-Krastanow growth mode, using compact metalorganic molecular-beam epitaxy (MOMBE) system. Results of structural analysis using AFM STM and TEM techniques for the QD shape, size and surface density are presented. The QDs grown in this work have truncated cone shape with average base diameter of 50nm and variable heights between 1nm to 4nm. High surface density of 4·1010cm-2 of self-assembled QDs was reached.   

A unique photoluminescence (PL) spectrum from these layers is composed of distinct spectral lines due to emission from QDs having the same monolayer-stepped height. This spectrum was analyzed in two manners. First the Gallium content of the InxGa1-xAs QDs was extracted by fitting the PL peak location to an 8 band K·P simulation results. Second, the question of lateral confinement effect on the electronic level locations is discussed with the aid of 3D one-band effective-mass approximation simulation. It is shown that the ground state of the QDs is not sensitive to the lateral confinement.

QD Infrared Pphotodetector was fabricated from the SAQDs layers in mesa and lateral structure. Results from interband and intraband photocurrent measurements show that the selection rules for intraband transitions are those expected from quantum wells.

Photocurrent spectroscopy reveals important new physical insights into the electronic structure of the In(Ga)As/InP QDs. A model for the electronic state location based on 8 band K·P simulation is used to explain the observed optical transitions as measured by photocurrent.