Room-temperature SiGe light-emitting diodes

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Abstract

In the present paper the electroluminescence of PIN diodes with either strained SiGe/Si or Ge islands in the i-region has been investigated experimentally and by quantitative modelling. The modelling helped to improve the diode structure. Consequently, diodes with strained Si0.80Ge0.20 could be improved so as to reveal emission up to room temperature, if the thickness was high enough. To overcome the thickness limitation due to plastic relaxation, we used selective epitaxy on small areas. We also present results for diodes with Ge islands in the active region. The internal quantum efficiency of light emitting diodes with strained SiGe was at room temperature ∼10−4, while diodes with islands emitted ten times less light.

Introduction

To have efficient SiGe light emitters for the optical communication wavelengths 1.3 and 1.55 μm much effort is still to be done to optimize the structure. The data published so far have shown that the performances of SiGe light-emitting diodes (LED) are limited by nonradiative recombination processes (usually Auger recombination) and recombination on deep traps. Electroluminescence (EL) near room temperature from Si1−xGex based PIN diodes was already observed from single and multiple quantum wells with x=0.3–1 1, 2, 3, 4and from superlattices [5].

Previously, we demonstrated LED with SiGe islands in the active region emitting at low-injection currents 100 times more than diodes with smooth strained SiGe layers. This was supposed to be due to a reduction of recombination on defects by the localization of holes in the islands [6]. We have also realized LEDs with strained SiGe layers [7], but 300 K operation was only possible for x⩾0.20 and by using strained layers much thicker than the critical thickness [8]. In this study, we present recent advances in the development of near infrared SiGe based emitters. The room-temperature EL could be significantly improved both for strained SiGe diodes as well as for diodes with Ge islands by decreasing the recombination at the buffer–substrate interface. For diodes with Ge islands, the room-temperature EL could be increased, as well, by using a Ge multilayer structure.

Section snippets

Experimental

The selective epitaxial growth (SEG) was carried out by low-pressure chemical vapour-deposition at 700°C and 0.12 T using SiCl2H2 and He-diluted GeH4 as source gases and H2 as carrier gas [9]. N+ (0 0 1) Si wafers were oxidized and patterned with square holes of different dimensions. The PIN diodes were of the type p+nn+ with the following layer sequence: (1) Si buffer, (2) SiGe (either thick Si0.80Ge0.20 or layers with Ge islands), (3) SiGe spacer (x=0.02) and (4) boron doped SiGe (x=0.02) 7, 8.

Results and discussion

LEDs with strained Si0.80Ge0.20 previously reported showed a strong decrease of the band-edge EL at T>100 K [7]. In order to increase the efficiency and operating temperature, simulations of the EL were performed [8]. When forward biased the diodes emit light in the near infrared. The emission is either due to interband transitions in strained samples or due to dislocations in relaxed samples. Fig. 1a presents two EL spectra at 150 K of diodes from the same epilayer, but one with an area of 1 mm2

Acknowledgements

The authors would like to thank C. Dieker for the TEM investigations. One of the authors T.S. is grateful to the Forschungszentrum Jülich and to the Alexander von Humboldt Foundation for financial support.

References (14)

  • Q. Mi et al.

    Appl. Phys. Lett.

    (1992)
  • S. Fukatsu et al.

    Appl. Phys. Lett.

    (1993)
  • M. Förster et al.

    J. Appl. Phys.

    (1996)
  • H. Presting et al.

    Appl. Phys. Lett.

    (1996)
  • J. Engvall et al.

    Appl. Phys. Lett.

    (1993)
  • R. Apetz et al.

    Appl. Phys. Lett

    (1995)
  • R. Apetz, L. Vescan, R. Loo, R. Carius, H. Lüth, in: Proc. 24th ESSDERC, C. Hill, P. Asburn (Eds.), Frontiers, 1994, p....
There are more references available in the full text version of this article.

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