Blue laser diodes by low temperature plasma assisted MBE
Polish Academy of Sciences, Institute of High Pressure Physics (UNIPRESS), Sokolowska 29/37, Warszawa 01-142, Poland
We present recent progress in growth of nitride based semiconductor structures made by plasma assisted MBE (PAMBE) for electronic components like laser diodes (LDs), high electron mobility transistors (HEMTs) and resonant tunneling diodes (RTDs). This technology is ammonia free and nitrogen for growth is activated by RF plasma source from nitrogen molecules. We describe new approach for growth of nitrides by PAMBE at low temperatures. The crucial for this technique is to use thin, dynamically stable, metal (In or Ga) layer on (0001) GaN surface, which significantly reduces barriers for N adatom diffusion enabling high quality 2D step-flow growth mode at low temperatures. We demonstrate importance of low threading dislocation (TDs) density substrates for high quality epitaxy in PAMBE. The gowth of nitrides on low TDs density bulk GaN substrates allows to achieve step-flow epitaxy with parallel atomic steps and eliminates problems related with formation of hillocks due to the dislocation mediated growth - e.g., a high mobility twodimensional electron gas at GaN/AlGaN interface (exceeding 110 000 cm2/Vs at 4.2 K) is achieved.
The new perspective for PAMBE in optoelectronics has been opened recently by a demonstration of blue–violet LDs . We show room temperature, continuous wave (cw) operation of InGaN multiquantum wells LDs made by PAMBE at 411 nm wavelength . The threshold current density and voltage were 4.2 kA/cm2 and 5.3 V respectively. High cw optical power output of 60 mW is achieved. The LDs were fabricated on low TDs density bulk GaN substrates at growth temperatures 600oC - 700oC.
In this work, we discuss also properties of InGaN/GaN quantum wells, p-type conductivity limits in GaN:Mg and InGaN:Mg layers and point out potential of PAMBE for UV and green emitters.
Acknowledgements: This work was partially supported by Polish Ministry of Science and Higher Education Grant Nr 3T11B04729
 C. Skierbiszewski, et. al., Appl. Phys. Lett. 88, 221108 (2006)
Presentation: Invited at E-MRS Fall Meeting 2007, Acta Materialia Gold Medal Workshop, by Czeslaw Skierbiszewski
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-06-19 12:49 Revised: 2009-06-07 00:44