Temperature Study of Photoluminescence from Deep CdTe/Cd_1-xMn_xTe Quantum Wells

Abstract

The photoluminescence studies in CdTe/CdMnTe quantum wells are reported in the temperature range 10-300 K. The MnTe concentration in the barriers is x = 0.3, 0.5, 0.63 and 0.68. Thus the potential wells in our samples are very deep, of the order of 800 meV in the conduction band and 200 meV in the valence band in the case of the x = 0.68 sample. In spite of the large lattice mismatch (related to high x value) between the wells and the barriers the observed line widths are as narrow as 2 meV in the case of 100 A. Clear manifestations of internal strain are observed. In particular, the temperature coefficient of the luminescence energies shows strong dependence on the width of wells.PACS numbers: 73.20. Dx, 78.55.Et Superlattices and quantum wells composed of diluted magnetic semiconductors (DMS) are studied for a decade now [1,2]. From many possibilities offered by DMS systems the most thoroughly investigated structures are those consisting of CdTe (quantum wells) and Cd1-x Mnx Te (barriers). In the majority of cases, the MnTe molar fraction in the structures studied so far was limited to x < 0.3 (superlattices involving pure cubic MnTe being an exception). The reasons for limiting the studies to small molar fractions were, probably, related to difficulties in preparation of quantum well structures of sufficient quality suitable for optical and magneto-optical investigations. These difficulties are related to a considerable lattice mismatch between CdTe and highly concentrated Cd 1 -x Mnx Te (αCdTe = 6.481 A, αcdMnTe = (6.481 -0.148x) A) which may result in formation of dislocations and other structural imperfections that reduce the optical quality . of the material.Here we present a study of a luminescence from a series of CdTe/Cd1-x Mnx Te quantum wells with MnTe molar fraction in barriers as high as x = 0.68. The samples studied by us were grown by molecular beam epitaxy on either GaAs(100) or CdTe(100) substrates. The growth was performed in EPI 620 apparatus at (500)

Luminescence Decay in Deep Quantum Wells CdTe/Cd0.5Mn0.5Te at Room Temperature

“…This iS in good agreement with more accurate spectral discrimination in Ref. [9]. The curves shown in Fig.…”

“…This finding is in agreement with the conclusion of the time resolved luminescence study of Polhman et al [2] who showed that in shallow Cd1-x MnxTe quantum wells only the low temperature (below 50 K) luminescence decay is limited by radiative recombination of excitons while at high temperatures τi is due to non-radiative recombination. Our conclusion concerning the non-radiative character of the mechanism which determines the luminescence decay at 300 K is also compatible with the fast decrease in the spectrally integrated intensity of the luminescence with increasing temperature found in [9] in this highest temperature range.…”

“…Further details of the luminescence study of this sample, including its temperature variation, can be found in Ref. [9]. The luminescence observed in [9] was shown to consist of at least two separate lines which can be ascribed to a free (or weakly localized) excitons and impurity-bound excitons.…”

Magnetic Characterization of Molecular Beam Epitaxy Grown Cd1xMnxTe Structures

“…Also, an enhanced paramagnetic contribution to the magnetic susceptibility at low temperatures has been found in CdTe/CdMnTe superlattice. The latter effect was assigned to the presence of isolated paramagnetic ions in the interface regions as a result of an intermixing of Mn and Cd ions and/or a smaller number of magnetic bonds at the interface.In this paper we report results of magnetic measurements performed on both thick (Cd 0.60 Mn0.40 Τe and MnTe) epilayer and CdTe/Cd 0.50Mn0.50 Te superlattices grown by MBE on GaAs substrates [3]. In order to reduce effects of (169)…”

“…In this paper we report results of magnetic measurements performed on both thick (Cd 0.60 Mn0.40 Τe and MnTe) epilayer and CdTe/Cd 0.50Mn0.50 Te superlattices grown by MBE on GaAs substrates [3]. In order to reduce effects of (169) the lattice mismatch, GaAs was buffered with 3 μm of CdTe.…”