D.R. Menke

Zinc-blende MnTe: epilayers and quantum well structures

Epilayers of the previously hypothetical zinc‐blende MnTe have been grown by molecular beam epitaxy. Epitaxial layers (0.5 μm thick) of MnTe were characterized using x‐ray diffraction and transmission electron microscopy; optical reflectance measurements indicate a band gap of ∼3.2 eV. A series of strained single quantum well structures was fabricated with zinc‐blende MnTe forming the barrier to CdTe quantum well regions; photoluminescence spectra indicate optical transitions corresponding to strong electron and hole confinement.

Influence of GaAs surface stoichiometry on the interface state density of as‐grown epitaxial ZnSe/epitaxial GaAs heterostructures

Epitaxial ZnSe/epitaxial GaAs interfaces have been formed by molecular beam expitaxy and evaluated by several techniques including capacitance‐voltage measurements. In the study reported here, the GaAs surface stoichiometry was systematically varied prior to the nucleation of ZnSe. A dramatic reduction of interface state density occurred when the GaAs epilayer was made As deficient. The resulting interface state densities of as‐grown structures are comparable to values obtained with (Al,Ga)As/GaAs interfaces.

Characterization of Ga2Se3 at ZnSe/GaAs heterovalent interfaces

Despite the valence difference across the junction, it has been shown that ZnSe/GaAs epilayer/epilayer interface state densities can be reduced to values comparable to the (Al,Ga)As/GaAs interface. We have previously reported a transmission electron microscopy study indicating that ZnSe/GaAs structures exhibiting low interface state densities are associated with the formation of an interfacial layer of zinc‐blende Ga2Se3. In this letter we describe a procedure whereby an interfacial layer can be deliberately introduced prior to nucleation of ZnSe. In situ x‐ray photoelectron spectroscopy is used to study the nature of the bonding at the interfacial layer. A comparison of the Se 3d core level features from the ZnSe epilayer surface, a Se‐reacted GaAs surface, and from a separately grown Ga2Se3 epilayer, clearly indicates the same Se bonding characteristic for the Se‐reacted interfacial layer and the Ga2Se3 epilayer.

An x-ray photoelectron spectroscopy study of bonding at II-VI/III-V heterovalent interfaces

In this paper in situ x‐ray photoelectron spectroscopy (XPS) is used to study the nature of the bonding at ZnSe/GaAs and CdTe/InSb interfaces grown by molecular‐beam epitaxy. X‐ray photoelectron spectra support the transmission electron microscopy evidence that ZnSe/GaAs MIS capacitors exhibiting low interface state densities are associated with the formation of an interfacial layer of zinc blende Ga2Se3. An interfacial layer can be deliberately introduced by reacting an As deficient GaAs surface with an incident Se flux. A comparison of the Se 3d core level features from the ZnSe epilayer surface, a Se‐reacted GaAs surface, and from separately grown Ga2Se3 epilayers, clearly indicate the same Se bonding characteristic for the Se‐reacted layer, and the Ga2Se3 epilayer. A parallel XPS study of CdTe/InSb interfaces leads to the conclusion that there is a general tendency for the formation of a III–VI interfacial compound when forming a II–VI‐on‐III–V junction.

Effect of GaAs surface reconstruction on interface state density of epitaxial ZnSe/epitaxial GaAs heterostructures

Epitaxial ZnSe/epitaxial GaAs interfaces have been grown using molecular beam epitaxy and evaluated by capacitance–voltage measurements and transmission electron microscopy. The GaAs surface stoichiometry was systematically varied prior to the nucleation of ZnSe. A significant reduction of interface state density occurred when the GaAs epilayer surface was As deficient. The resulting interface state densities of as‐grown structures are comparable to values obtained with (Al,Ga)As/GaAs interfaces.

Pseudomorphic ZnTe/AlSb/GaSb heterostructures by molecular beam epitaxy

A series of pseudomorphic ZnTe/AlSb/GaSb epilayer/epilayer heterostructures, aimed at the realization of novel wide band‐gap light‐emitting devices, was grown by molecular beam epitaxy. The structures were evaluated by several techniques including transmission electron microscopy (TEM), x‐ray rocking curves, photoluminescence (PL), and Raman spectroscopy. Reflection high‐energy electron diffraction intensity oscillations were observed during nucleation of ZnTe. The presence of dislocation‐free pseudomorphic structures was confirmed by TEM. The PL spectra of ZnTe epilayers showed dominant near‐band‐edge features composed of free and shallow impurity bound excitons.

Quantum wells with zincblende MnTe barriers

In this paper we describe a series of MnTe/CdTe/MnTe and MnTe/InSb/MnTe single quantum well structures. For the CdTe quantum wells we report the observation of luminescence covering the entire visible range from red to blue; a quantized state in the InSb well is used to implement resonant tunneling. X-ray diffraction and transmission electron microscopy (TEM) were used to evaluate the microstructural quality of the structures. Dark-field TEM showed that, in spite of the 2.3% lattice mismatch, the MnTe layers remained pseudomorphic and dislocation-free. High resolution images (also used to determine dimensional details) indicated that the interfaces were atomically abrupt, and that the CdTe and InSb wells were essentially unstrained in each of the structures; most of the strain was contained in the MnTe barrier layers. Optical properties of the single quantum well structures have been studied using photoluminescence and photoluminescence excitation spectroscopy. Blue luminescence at 2.59 eV (n = 1 transition) has been observed from a structure with a 10 A CdTe well. The negative differential resistance observed from MnTe/InSb resonant tunneling structures represents, to our knowledge, the first report of a dimensionally quantized state in InSb.

ZnSe/GaAs heterovalent interfaces: interface microstructure versus electrical properties

Abstract Epitaxial ZnSe/epitaxial GaAs interfaces are formed by molecular beam epitaxy and evaluated by several techniques including capacitance-voltage ( C-V ) measurements. The GaAs surface stoichiometry is systematically varied prior to the nucleation of ZnSe. A dramatic reduction of interface state density occurred when the GaAs epilayer is made As deficient. The ZnSe/GaAs interfaces exhibiting low interface state densities are associated with the presence of an interfacial layer of zincblende Ga 2 Se 3 . In situ X-ray photoelectron spectroscopy (XPS) is used to study the nature of the bonding at the interfacial layer. The character of Se 3d core level features from the interfacial region and from separately grown Ga 2 Se 3 epilayers support the identification of the interfacial layer as Ga 2 Se 3 .

Spectroscopy in CdTe/MnTe and ZnTe/MnTe single quantum wells : new binary wide gap II-VI heterostructures

Abstract With the incorporation of cubic zincblende MnTe, a range of optical studies have been carried out on single quantum wells of ZnTe/MnTe and CdTe/MnTe. By using thin MnTe barrier layers the structures appear to be nearly pseudomorphic and show evidence for good electron-hole confinement.

Strong confinement effects in CdTe/MnTe quantum wells: A new strained layer binary II-VI heterostructure

Abstract A range of optical studies have been carried out on a series of single quantum wells of CdTe/MnTe. The structures appear to be nearly pseudomorphic and show evidence for robust electron-hole confinement. Exciton states have been characterized in terms of lifetime and coupling to optical phonons.