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Publication Detail
Maximising the gain: optimising the carrier distribution in InGaAs quantum dot lasers
  • Publication Type:
  • Authors:
    Smowton PM, Sandall IC, Mowbray DJ, Liu HY, Hopkinson M
  • Publisher:
    SPIE - The International Society for Optical Engineering
  • Publication date:
  • Place of publication:
    Bellingham, US
  • Pagination:
  • Published proceedings:
    Proceedings of SPIE
  • Volume:
  • Editors:
    Osinski M,Henneberger F,Arakawa Y
  • Status:
  • Language:
  • Keywords:
    laser diodes; quantum dots
  • Notes:
    The conference Physics and Simulation of Optoelectronic Devices XV took place on Monday 22 January 2007 in San Jose, California, USA
The performance of lasers with self assembled quantum dot active regions is significantly affected by the presence of the two dimensional wetting layer and the other states necessary for carrier injection due to the manner in which carriers are distributed amongst the various states. In this work we describe three approaches to overcome the low value of maximum saturated gain, which has been observed by many groups worldwide, and explain the approaches in terms of the impact on the distribution of carriers within the available states. We present results of direct measurements of the modal gain and measurements that indicate the form of the carrier distribution within the samples to justify our argument. The structures examined include the use of a high growth temperature to smooth the matrix layer, the use of p-type modulation doping and the use of InAlAs capping layers and all have been grown by solid source molecular beam epitaxy. We demonstrate CW operation at 1.3μm for 1mm long devices with uncoated facets and very low threshold current density (< 40Acm-2) in longer devices. We also demonstrate that the negative T0 (reducing threshold current density with increasing temperature) obtained around room temperature in our p-doped devices is due to the temperature dependence of the gain.
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