Study of the properties of the intrinsic point defects in monocrystalline germanium

Title: Study of the properties of the intrinsic point defects in monocrystalline germanium

 

Promoters : 

Freddy Callens (EMR) – Eddy Simoen (imec) – Jan Vanhellemont (DiSC) – Henk Vrielinck (DiSC)

 

Type: FWO – research project (4 years)

 

Duration :01/01/2010 – 31/12/2013

 

Summary :

In this project we study thermodynamic properties of intrinsic point defects in Ge, e.g. formation energy thermal solubility, diffusivity and recombination probability. The so-called “quenching” method is used, in which equilibrium concentrations of defects at high temperatures are frozen in by rapidly cooling the sample. During the quench, acceptors are formed which alter the resistivity of the sample. Using resistivity and Hall measurements at various temperatures, these changes in the resistivity and type of the semiconductor can be monitored as a function of anneal temperature and the initial properties (e.g. doping and impurities) of the sample. The quenched-in defects are studied using spectroscopic techniques (DLTS, PTIS, FTIR and EPR) in order to determine their structure, chemical composition and electrical properties. In this way changes in the resistivity can be linked to equilibrium concentrations of vacancies (and/or interstitials) at the anneal temperature before the quench. In this way we aim to determine the formation energy and solubility of the vacancy and the influence of dopants and imputities in Ge on these parameters. In addition, measurements and simulations of concentration depth profiles for the quenched-in defects provide information on diffusivity and recombination of the intrinsic point defects.