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

Lead Research Organisation: Lancaster University
Department Name: Physics


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.


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Description We systematically investigated the incorporation of nitrogen from the liquid phase into both InAs and GaSb using a variety of solid sources. We found that the maximum amount of N which we could successfully introduce into InAs from the liquid phase was 0.5% using GaN which was the most effective source. Similar results were obtained for LPE of GaSbN. Photoluminescence emission was observed from these materials in the mid-infrared spectral range, confirming that LPE can be used to prepare dilute nitrides with low N content. We also observed bandgap narrowing due to the incorporation of Bi in GaSb. We obtained a band gap reduction upto 78 meV with 1.5 wt% Bi added to a Ga+GaSb growth melt.
We successfully demonstrated the MBE growth of InAsN and InAsNSb dilute nitrides and obtained photoluminescence across the mid-infrared spectral range. The addition of small amounts of Sb was found to enhance the N incorporation and also significantly improved the optical quality of these materials. In collaboration with researchers at Nottingham, Wroclaw and Taiwan we successfully obtained new fundamental information about carrier transport and band structure including information about residual carrier concentration, effective mass and spin orbit splitting and their dependence on N content.
This visiting fellowship was very successful and resulted in 7 publications in refereed journals, including 3 in APL as well as 12 conference presentations, and contributed to the training of 1 PhD student.
Exploitation Route We demonstrated InAsSbN/InAs quantum wells which exhibited mid-infrared emission consistent with a type I band alignment and which is an important result for subsequent device fabrication.
Sectors Digital/Communication/Information Technologies (including Software),Electronics

Description The outcomes of the research arising from this visiting fellowship were used to help secure follow on funding and helped pave the way for further research on dilute nitride materials and devices.
First Year Of Impact 2012
Sector Education
Description Responsive mode grant - InAsNSb Dilute Nitride Materials for Mid-infrared Devices & Applications
Amount £370,325 (GBP)
Funding ID EP/J015849/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 07/2012 
End 03/2016
Description Responsive mode grant - dilute nitride type II QD solar cells
Amount £401,100 (GBP)
Funding ID EP/G070334/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 11/2009 
End 10/2012
Description H M Government Communications 
Organisation Her Majesty's Government Communications
Country United Kingdom 
Sector Public 
PI Contribution samples for evaluation
Collaborator Contribution validation of samples and input to specifications
Impact knowledge exchange
Start Year 2008
Description Kidde PLC 
Organisation Kidde PLC
Country United States 
Sector Private 
Start Year 2008
Description National Taiwan University 
Organisation National Taiwan University
Country Taiwan, Province of China 
Sector Academic/University 
Start Year 2008
Description Open days 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Our research was showcased to sixth form students and also members of the general public on visit days and open lab days by our postdocs and research students throughout the year. Activities involved short explanatory talks and lab tours including question and answers.

UCAS applications to Lancaster Physics have increased partly as a result of our outreach programme.
Year(s) Of Engagement Activity Pre-2006,2006,2007,2008,2009,2010,2011,2012,2013,2014