Characterisation Of Quantum Wells By Auger Analysis On Chemical Bevels
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CHARACTERISATION OF QUANTUM WELLS BY AUGER ANALYSIS ON CHEMICAL BEVELS
JEAN OLIVIER,
P.ETIENNE,
M.RAZEGHI,
P.ALNOT.
THOMSON-CSF - L.C.R. Domaine de Corbeville 91401 ORSAY - France -
ABSTRACT
In recent papers, we have described a depth profiling method using chemical beveling and Auger line scan measurement, quick and easy to perform, with a sufficient resolution to check the abruptness of chemical interfaces obtained in epitaxial growth of III-V compounds. The variation law of chemical species concentrations at the interfaces is tighly related to the mecanisms of initial growth. We present here a theoretical analysis applied to chemically beveled interfaces with sharply graded concentrations. We show on two examples of LP-MOCVD quantum wells (InP/GaInAs/InP and GaInP/GaAs/GaInP) the good agreement between experimental and theoretical curves, assuming exponentially varying concentrations. Finally, we discuss the correlations with the dynamics of the first steps of the LP-MOCVD growth.
INTRODUCTION Understanding the initial stage of epitaxial growth is essential to build heterostructures such as heterojunctions (HJ), quantum wells (QW) or superlattices ( SL ) where interfaces between layers play a prominent part in their optical and electrical capabilities. For example physical studies of the chemical species concentrations at the interfaces, can give valuable informations on the initial steps of epitaxial growth. The theoretical calculations of Auger currents given by Auger line scan measurements on chemically beveled heterostructure are performed, assuming exponentially varying concentrations at the interface and compared with experimental curves the agreement is good for two exemples of low pressure metalorganic chemical vapor deposition (LP-MOCVD) quantum wells (InP/GaInAs/InP and GaInP/GaAs/GaInP).
Mat. Res. Soc. Symp. Proc. Voa. 91. 11987 Materials Research Society
498
EXPERIMENTAL 1) Combined with ion etching, AES can be used to get elemental concentraNevertheless several factors affect the tion profiles within overlayers. resolution depth. We can classify the most important mechanisms which broaden the concentration profiles into two classes : - Auger electron escape depth and ion bombardement effects ( ion knock-on mixing, preferential sputtering and ion-induced roughness). In order to get round the disadvantages of ion milling, we have developped a method of chemical beveling coupled with line scan Auger measurements to check interfaces of epitaxial III-V compounds[lJ. This method consists of making a chemical bevel to bring to the exposed surface all layers and interfaces, and then scanning the primary electrons of our scanning Auger apparatus along the bevel and collecting data associated with every Auger energy specified. The chemical bevels are produced by a technique in which the liquidliquid interface between pure methanol and a bromine-methanol solution is raised progressively over de sample. The bevel angle c can be controlled by the speed of the etching solution flow up the sample, and
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