Composition related electrical active defect states of InGaAs and GaAsN

This paper discusses results of electrically active defect states - deep energy level analysis in InGaAs and GaAsN undoped semiconductor structures grown for solar cell applications. Main attention is focused on composition and growth condition dependent impurities and the investigation of their possible origins. For this purpose a widely utilized spectroscopy method, Deep Level Transient Fourier Spectroscopy, was utilized. The most significant responses of each sample labelled as InG2, InG3 and NG1, NG2 were discussed in detail and confirmed by simulations and literature data. The presence of a possible dual conduction type and dual state defect complex, dependent on the In/N composition, is reported. Beneficial characteristics of specific indium and nitrogen concentrations capable of eliminating or reducing certain point defects and dislocations are stated

AP-MOVPE Technology and Characterization of InGaAsN p-i-n Subcell for InGaAsN/GaAs Tandem Solar Cell

Tandem (two p-n junctions connected by tunnel junction) and multijunction solar cells (MJSCs) based on AIIIBV semiconductor compounds and alloys are the most effective photovoltaic devices. Record efficiency of the MJSCs exceeds 44% under concentrated sunlight. Individual subcells connected in series by tunnel junctions are crucial components of these devices. In this paper we present atmospheric pressure metal organic vapour phase epitaxy (AP-MOVPE) of InGaAsN based subcell for InGaAsN/GaAs tandem solar cell. The parameters of epitaxial structure (optical and electrical), fabrication process of the test solar cell devices and current-voltage (J-V) characteristics are presented and discussed

The influence of quantum well and barrier thicknesses on photoluminescence spectra of InGaAs/AlInAs superlattices grown by LP-MOVPE

In the presented work, the influence of the quantum well and barrier thicknesses on optical characteristics of InGaAs/AlInAs superlattices was reported. Six different structures of In0.53Ga0.47As/Al0.48In0.52As superlattices lattice-matched to InP were grown by low pressure metal organic vapour phase epitaxy (LP-MOVPE). Optical properties of the obtained structures were examined by means of photoluminescence spectroscopy. This technique allows quick, simple and non-destructive measurements of radiative optical transitions in different semiconductor heterostructures.The analysis of recorded photoluminescence spectra revealed the influence of the quantum well and barrier thicknesses on the emission line energy

Heat Dissipation Schemes in AlInAs/InGaAs/InP Quantum Cascade Lasers Monitored by CCD Thermoreflectance

In this paper, we report on the experimental investigation of the thermal performance of lattice matched AlInAs/InGaAs/InP quantum cascade lasers. Investigated designs include double trench, single mesa, and buried heterostructures, which were grown by combined Molecular Beam Epitaxy (MBE) and Metal Organic Vapor Phase Epitaxy (MOVPE) techniques. The thermal characteristics of lasers are investigated by Charge-Coupled Device CCD thermoreflectance. This method allows for the fast and accurate registration of high-resolution temperature maps of the whole device. We observe different heat dissipation mechanisms for investigated geometries of Quantum Cascade Lasers (QCLs). From the thermal point of view, the preferred design is the buried heterostructure. The buried heterostructures structure and epi-layer down mounting help dissipate the heat generated from active core of the QCL. The experimental results are in very good agreement with theoretical predictions of heat dissipation in various device constructions