MOVPE Growth and Device Applications of Ternary and Quaternary Dilute Bismide Alloys on GaAs Substrates

Abstract

III/V semiconductors containing bismuth (Bi) show some interesting properties for high efficient optoelectronic applications in the near- and mid-IR region. However, the alloys are highly metastable due to the large covalent radius of the Bi atom compared to the other group V atoms, which are replaced in the cubic zinc-blende lattice. Hence, carefully adjusted growth conditions at low growth temperatures are required in order to incorporate a significant amount of Bi into the host lattice. In this book chapter, we review our current understanding of the growth of dilute Bi-containing III/V semiconductor alloys on GaAs substrates, the factors, which limit the Bi incorporation, as well as the application of the material in electrically pumped LASER diodes. Bi fractions of up to 4.2% Bi and 7% Bi can be achieved using metal-organic vapor phase epitaxy (MOVPE) as growth technique using pulsed as well as continuous flow conditions, respectively. The influence of different growth conditions, i.e., the growth temperature and partial pressures of the used precursors are investigated and the results are discussed in detail. Exceeding a critical Bi concentration, accumulation of metal droplets on the surfaces is found which hampers high-quality growth of subsequent layers, which is however necessary for devices. This limitation in the Bi incorporation makes quaternary alloys, like GayIn1−yAs1−xBix structures on GaAs substrates interesting for optoelectronic applications. Optimization of the material quality resulted in the demonstration of electrically pumped GaAs1−xBix laser diodes with up to 4.1% Bi operating at room temperature. As there is this current upper limit of 7% Bi incorporation using MOVPE growth, we discuss factors, which might influence and limit the Bi incorporation in the host material. The use of alternative Bi precursors is investigated with regard to the impact of different carbon (C)-containing radicals on the surface. The impact of strain on the Bi incorporation is discussed by adding nitrogen or phosphorus and hence tensilely prestraining the layer. Finally, we also investigate the influence of trimethylindium (TMIn) on the Bi incorporation in GayIn1−yAs1−xBix and compare its growth to the one of GaAs1−xBix.