,ouw,uo~ CRYSTAL aROWTH ELSEVIER Journal of Crystal Growth 184/185(1998)936-941 Excitons in Cd,_,Mn,Te quantum wells with a parabolic confining potential T. Wojtowicza3*, M. Kutrowskia, G. Cywir’xki”, G. Karczewski”, E. Janik”, E. Dynowska”, J. Kossuta, R. Fiederlingb, A. Pfeuffer-Jeschkeb, W. Ossaub a Institute of Physics, Polish Academy of Sciences, Al. Lotnikdw 32146, 02-668 Warsaw, Poland bPhysikalisches Institut der Universitiit Wiirzburg, D-97074 Wiirzburg, Germany Abstract Excitons in Cd1 _,Mn,Te and Cd1 __,Mg,Mn,Te parabolic and half-parabolic quantum wells are investigated by magnetooptical methods. The diagonal and nondiagonal (in the harmonic oscillator quantum numbers) transitions are observed. Apart from 1s excitons we observed also 2s and 3s states in the presence of a magnetic field. The results are discussed in terms of a simple variational calculation of the exciton energy. It is shown that a parabolic confining potential very effectively reduces the dimensionality of the excitons leading to large values of their binding energy even in relatively wide quantum wells. The truly parabolic shape of the confining potential in the investigated structures is proved by an analysis of spin splitting of the exciton states. 0 1998 Elsevier Science B.V. All rights reserved. PACS: 73.20.D~; 78.55.Et Keywords: Excitons; Parabolic quantum wells; Diluted magnetic semiconductors; Magnetooptical studies of low dimensional structures 1. Introduction One of the most interesting reasons for a recent interest in semiconductor quantum wells with a parabolic shape of the confining potential (for a review see Ref. [ 11) is a strong enhancement of the exciton binding energy in such structures. Surpris- *Corresponding author. Fax: + 48 22 430926; e-mail: wojto@ifpan.edu.pl. ingly, there are hardly any papers devoted to this problem, although the excitonic features observ- able in parabolic quantum wells (PQWs) are very sharp reflecting a strong concentration of the oscil- lator strength for optical transitions between well- defined energy levels: apart from a short theoretical study [2] only one paper [3] mentions explicitly observation of the 2s excitonic peak in a PQW made of Ga, _.Al,As. The present paper reports on the investigation of excitons in parabolic and half-parabolic quan- tum wells (HPQW) made of II-VI materials 0022-0248/98/$19.00 c 1998 Elsevier Science B.V. All rights reserved PII SOO22-0248(97)00721-5