Liquid Phase Epitaxial Growth of Dilute Nitrides for the Mid-infrared - Visiting Fellowship for S. Dhar

We are interested in the incorporation of nitrogen into semiconductors such as GaAs, InAs and GaSb. This is important because the band gap of the parent III/V semiconductor is substantially reduced by the incorporation of very small amounts of nitrogen. These so-called dilute nitrides show promise for use in tailoring the wavelength and efficiency of novel semiconductor lasers and other optoelectronic devices. Although GaAsN and InGaAsN are currently being studied mainly for their applications in photodetectors and lasers in the 1.3 to 1.55 um telecomms wavelength range there is far less research into dilute nitride compounds for the mid-infrared (2-5 um) spectral range which is rich in applications. However, there are problems associated with incorporation of N and degradation of the crystalline quality and especially as nitrogen content in the material is increased beyond 1%. This project seeks to investigate the growth of dilute nitrides for the mid-infrared spectral range using growth from the liquid phase rather than from the gas phase.One key advantage of this approach is that we do not need any N plasma to introduce the nitrogen atoms and so we can avoid all the damage from the energetic N ion species generated as a by-product from the plasma source normally used in vapour phase growth. Liquid phase epitaxy (LPE) is well known to produce material of excellent crystalline perfection. The proposed project seeks to build on our existing expertise in LPE growth and mid-infrared optoelectronics at Lancaster and study the resulting material properties of GaAsN, InAsN, GaSbN with a view towards evaluating their potential for use in mid-infrared optoelectronic devices. We aim to investigate both bulk materials and also corresponding dilute N nanostructures. The preparation of dilute N III-V alloys with high quantum efficiency would be a real breakthrough, particularly for use within mid-infrared light sources and detectors for which there are many practical applications. Moreover, if the approach proves successful it can be readily extended to other technologically important alloys such as InGaAsN and GaAsPN.