IOP PUBLISHING SEMICONDUCTOR SCIENCE AND TECHNOLOGY Semicond. Sci. Technol. 23 (2008) 075028 (5pp) doi:10.1088/0268-1242/23/7/075028 Ion irradiation induced nitrogen mobility in a GaInNAs quantum well laser Y N Qiu 1 , G Papaioannou 2 , J Pozo 1 , J M Rorison 1 , M Saarinen 3 , J Konttinen 3 , J Viheri¨ al¨ a 3 , P Leinonen 3 , T Jouhti 3 and M Pessa 3 1 Room 2.14 Queen’s Building, Department of Electrical Electronic Engineering, University of Bristol, Bristol, BS8 1TR, UK 2 Solid State Physics Section, Physics Department, University of Athens, Athens 15784, Greece 3 Optoelectronics Research Centre, Tampere University of Technology, Tampere, PO Box 692, FIN-33101, Finland E-mail: yingningqiu@yahoo.com Received 25 January 2008, in final form 17 April 2008 Published 23 May 2008 Online at stacks.iop.org/SST/23/075028 Abstract Changes in the optical properties in GaInNAs/GaAs quantum wells after alpha particle bombardment followed by low temperature annealing are reported. Both blue and red shifts of the lasing wavelength are observed under different annealing conditions. This differs from the usually observed blue shift which is found after high-temperature post-grown annealing. Competing processes that result in the lasing wavelength shifts are energetic considerations which act to increase the number of Ga–N and In–As bonds (maximize the cohesive energy), minimizing the strain of the system which increases the number of In–N and Ga–As bonds (large-ion-small-ion links), maximizing the number of N located at lattice sites effective at shrinking the band-gap and moving the N position within the quantum well. For the case of high-temperature post-grown annealing the increase of Ga–As and In–N bonding wins, resulting in the blue shift observed. The wavelength shifts are discussed in terms of these competing mechanisms. 1. Introduction Dilute-nitride semiconductors based on GaInNAs/GaAs quantum well (QW) structures have attracted attention for their potential applications in optoelectronic devices [1]. Post- growth annealing has proved to be necessary to obtain high optical emission intensity, but results in an undesirable blue shift of the peak emission wavelength. For this reason, much work has been done to understand the mechanisms responsible for this blue shift leading to various and conflicting possible explanations. Amongst these, some support that neither In nor N diffuse out of the QW [2–4], although others suggest that both atoms do [5–7]. Other studies appear to show that only the In diffuses out of the QW [8, 9], while other observations support that only N diffuses out of the QW [10]. The diffusion issue led also to an uncertainty as to whether it occurs entirely within the QW on the order of a few atomic lengths [11] or through a nearest-neighbour relaxation involving interstitial–substitutional positions [2, 12]. The effect of electron radiation induced defects and subsequent annealing on the blue shift has been also investigated [13]. Monte Carlo simulations [14] show that theoretically the most stable state is that which increases the number of Ga–As and In–N bonds and this predicts a blue shift. This results from a competition of cohesive energy and strain effects. Finally, theoretical calculations based on the band-anti-crossing (BAC) model have shown that the blue shift can be also connected to the redistribution of nitrogen atoms in the QW [15]. Recent work on bulk GaInNAs annealed at a higher temperature than reported here, but still low relative to the usual QW annealing, has reported [16] an observed PL red shift which has been attributed to N moving from interstitial to site locations following the irradiation and annealing (There is no consideration of whether the N becomes bonded to In or Ga or indeed how this changes with annealing temperature.) This has been attributed to the N only being able to interact with the GaInAs conduction band and push it down when the N is located at a lattice site. These results show that short range ordering effects within the GaInNAs/GaAs QW can 0268-1242/08/075028+05$30.00 1 © 2008 IOP Publishing Ltd Printed in the UK