Electronic Structure Of Ⅲ-Ⅴ Narrow Gap Antimonide And Dilute-bismuth Semiconductors Studied By Infrared Modulation Spectroscopy

As powerful spectroscopy techniques, photoluminescence(PL) and photoreflectance(PR) are both nondestructive, convenient and of high sensitivity, and have been widely used in the electronic structure and optical properties studies of semiconductors. Benefited from the advantage of Fourier transform infrared(FTIR) spectrometer, the recent FTIR spectrometer-based infrared modulation PL and/or PR methods successfully eliminate the background thermal emission disturbance, significantly enhance the signal intensity, and promote the detectable spectral wavelength up to 20 μm.Besides Hg1-xCdxTe(MCT), antimonide is another important narrow-gap material because of its advantages of easy growth, low impurity density and high uniform.Meanwhile, as a wide-concerned material, dilute-bismuth(Bi) semiconductor manifests the behavior of large bandgap narrowing, low bandgap-temperature sensitivity and low influence on electron, which make it promising for infrared applications. However, the electronic structures and optical properties of actual material are usually affected by the impurities/defects and low-dimensional interface quality. Therefore, to improve/optimize the devices properties, the relations of the electronic structure and material condition for antimonide and dilute-Bi semiconductors are investigated in this thesis.The FTIR-based infrared modulation PL and PR methods are used to study the electronic structure and carrier transitions behavior of In Sb epitaxial layer, In As/Ga Sb superlattice, In Ga Sb/In As/Al Sb quantum wells(QWs) and dilute Bi semiconductors.In addition, the investigations of In PBi and Ga As(Sb)/In As quantum antidots(QADs)are also carried out. The main research is listed as following:(i) We use infrared PL and/or PR to study the electronic structure and carrier nature of In Sb epitaxial layer, In As/Ga Sb superlattice with In Sb-like interfaces and InGa Sb/In As/Al Sb QWs with In Sb- and Ga As-like interfaces. The positions of near bandedge binding and resonant levels in In Sb epitaxial layer are conformed by temperaturedependent PR. Then we use temperature- and excitation-dependent PL to investigate the post-growth annealing temperature effect on In As/Ga Sb superlattice with In Sb-like interfaces. The phenomenological model of temperature-induced interface atom interdiffusion is built to understand the relationship of the interface unsharpness and the carrier nonradiative recombination. What’s more, the carriers transitions behaviors in In Ga Sb/In As/Al Sb QWs with In Sb- and Ga As-like interfaces are studied by magnetoPL. The results indicate that the delocalized PL from the QWs with In Sb-like interfaces manifest the type-I and type-II transitions simultaneously because of the In Sb-like interface band alignment.(ii) The effects on interface structure, electronic levels and Auger recombination due to Bi incorporation in Ga Sb(Bi)/Al0.2Ga0.8Sb single QWs are investigated by infrared modulation spectroscopy. The terrace-like interface structures are introduced in Ga Sb Bi QW grown at either 360 or 380?C. Bi induces the crystal disorder in 360?C grown sample and the isoelectric Bi incorporation is negligible; while Bi are incorporated into V site in 380?C grown sample and it leads to the bandgap narrowing.The variation of the exciton nature in dilute-Bi QWs results from the Bi incorporation and crystal disorder. Meanwhile, PR result shows that both conduction band minimum(CBM) downshift and valence band maximum(VBM) upshift contribute to the Bi-induced bandgap reduction in Ga Sb1-xBix. The CBM downshift is(29±6)% for the bandgap narrowing, which indicates that while the valence band anticrossing(BAC) is dominant for the Ga Sb Bi bandgap reduction, the CBM downshift should not be overlooked. Moreover, the Auger recombination suppression due to Bi incorporation in Ga Sb Bi QW is also examined by the temperature- and excitation-dependent PL.(iii) We undertake the infrared PL investigation of In P1-xBixand Ga As(Sb)/In As QADs. We observed the below-gap PL features in the range of 0.5-1.2 e V in In PBi.The energies of those PL features are insensitive to the Bi content and temperature. By the preliminary analysis, the PL features in In PBi may come from the transitions from the P antisite(PIn) donor levels to the Bi cluster levels with different configurations.Also, the PL feature may be related to the Bi3+occupation in III site, which needs further investigation. Meanwhile, Si-doped Ga As(Sb)/In As QADs show a PL feature at about 0.45 e V, whose evolution against temperature indicates that it may comes from the compressive In As bandgap transition. The electron injection in In As due to the Sidoping enhances that PL feature and it becomes observable in PL spectra.