Using first‐principles band‐structure theory we have systematically calculated the (i) alloy bowing coefficients, (ii) alloy mixing enthalpies, and (iii) interfacial valence‐ and conduction‐band offsets for three mixed‐anion (CuInX2, X=S, Se, Te) and three mixed‐cation (CuMSe2, M=Al, Ga, In) chalcopyrite systems. The random chalcopyrite alloys are represented by special quasirandom structures (SQS). The calculated bowing coefficients are in good agreement with the most recent experimental data for stoichiometric alloys. Results for the mixing enthalpies and the band offsets are provided as predictions to be tested experimentally. Comparing our calculated bowing and band offsets for the mixed‐anion chalcopyrite alloys with those of the corresponding Zn chalcogenide alloys (ZnX, X=S, Se, Te), we find that the larger p−d coupling in chalcopyrite alloys reduces their band offsets and optical bowing. Bowing parameters for ordered, Zn‐based II‐VI alloys in the CuAu, CuPt, and chalcopyrite structures are present...

Band offsets and optical bowings of chalcopyrites and Zn‐based II‐VI alloys

Elastic, electronic and optical properties of ZnS, ZnSe and ZnTe under pressure

Refractive indices of semiconductors from energy gaps

We have fabricated boron carbide thin films on Si(111) and other substrates by plasma‐enhanced chemical‐vapor deposition (PECVD). The PECVD of boron carbides from nido‐cage boranes, specially nido‐pentaborane(9) (B5H9), and methane (CH4) is demonstrated. The band gap is closely correlated with the boron to carbon ratio and can range from 0.77 to 1.80 eV and is consistent with the thermal activation barrier of 1.25 eV for conductivity. We have made boron carbide by PECVD from pentaborane and methane that is sufficiently isotropic to obtain resistivities as large as 1010 Ω cm at room temperature. This material is also shown to be suitable for photoactive p‐n heterojunction diode fabrication in combination with Si(111).

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Characterization of boron carbide thin films fabricated by plasma enhanced chemical vapor deposition from boranes

Spectroscopic ellipsometry: a historical overview

Epitaxial AlxGa1−xAs structures whose compositions x vary continuously with thickness according to a given input function have been grown by chemical‐beam epitaxy under closed‐loop ellipsometric control. 200‐ and 500‐A parabolic quantum wells analyzed by photoreflectance and secondary‐ion mass spectrometry, respectively, show that actual compositions follow target values to within 0.02 in x. Growth of the 200‐A profile was controlled using compositions ellipsometrically determined for the outermost running 3.1 A (∼1 monolayer) of depositing material.Epitaxial AlxGa1−xAs structures whose compositions x vary continuously with thickness according to a given input function have been grown by chemical‐beam epitaxy under closed‐loop ellipsometric control. 200‐ and 500‐A parabolic quantum wells analyzed by photoreflectance and secondary‐ion mass spectrometry, respectively, show that actual compositions follow target values to within 0.02 in x. Growth of the 200‐A profile was controlled using compositions ellipsometrically determined for the outermost running 3.1 A (∼1 monolayer) of depositing material.

Growth of AlxGa1−xAs parabolic quantum wells by real‐time feedback control of composition

We report a systematic study of the optoelectronic properties of ZnSe1−xTex alloys grown by molecular beam epitaxy over the entire range of compositions. The band‐gap energy as a function of the composition presents a minimum at x≂0.65. The main luminescence emission observed at 5 K becomes narrower and closer to the band‐gap energy as we increase the Te content. The linewidth and the difference between the emission peak and band‐gap energy decrease significantly with increasing x and present a break in the slope at x≂0.65.

Evolution of the band gap and the dominant radiative recombination center versus the composition for ZnSe1−xTex alloys grown by molecular beam epitaxy

Interface Control in GaAs/GalnP Superlattices Grown by OMCVD

The authors address the principal materials for the design of a ZnSe-based visible injection laser: the controlled p-type doping of ZnSe and the development of heterostructures for optical and carrier confinement. Diode I-V characteristics of ZnSe p-n homojunctions are presented to demonstrate the existence of p-type ZnSe layers doped with lithium. These diodes exhibit electroluminescence in the visible range. Growth of the II-VI quaternary Zn1-yCdySe1-xTex is reported for the first time. Along with tuning of the bandgap energy with composition, these quaternary alloys are expected to provide tuning of the band offsets with ZnSe, thus having great potential for the design of practical visible heterostructure lasers.

MBE growth of the (Zn,Cd)(Se,Te) system for wide-bandgap heterostructure lasers

We report properties of the InAlAs/InP interface and its formation during growth by organometallic molecular beam epitaxy. Taking advantage of the photoluminescence emission occurring at this type II interface, we were able to directly investigate the interface characteristics for different growth conditions. A shift is observed in the energy of the interface recombination transition which we interpret as evidence of a P‐As exchange effect dependent on the specific growth sequence. This effect was further investigated by growing interfaces with thin layers (InAs, AlAs, AlP) between the InP and InAlAs. The results can be understood in terms of a model based on bond strength considerations. We predicted and demonstrated that the most stable interface is obtained with incorporation of a thin AlP interfacial layer.

M. J. S. P. Brasil

Papers

Growth of AlxGa1−xAs parabolic quantum wells by real‐time feedback control of composition

Evolution of the band gap and the dominant radiative recombination center versus the composition for ZnSe1−xTex alloys grown by molecular beam epitaxy

Interface Control in GaAs/GalnP Superlattices Grown by OMCVD

MBE growth of the (Zn,Cd)(Se,Te) system for wide-bandgap heterostructure lasers

Optical transitions and chemistry at the In0.52Al0.48As/InP interface