Visible Photoluminescence from Silicon Nanoconstrictions formed by Heavy Hydrogen Implantation and Annealing Treatments
- PDF / 414,584 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 9 Downloads / 186 Views
INTRODUCTION Efficient light emission from silicon based systems has been widely reported. To look for new systems from which efficient light emission could be achieved the key-points are: passivation, short-range scale crystallinity and confinement.. A prototypical system can be considered namely porous-silicon 1 where one gets carrier confinement by anodic HF dissolution of Si with the formation of small Si nanocrystals where room temperature visible emission occurs. The H in the solution produces the passivation of the Si nanocrystals removing non-radiative recombination paths. Other systems can be considered as well, e. g. hydrogenated amorphous Si or Erdoped Si. In this paper, we present another system where we discovered visible emission early this year. 2 The simultaneous presence of microcavities and H passivating atoms permits the formation of small Si regions among the microcavities (nanoconstrictions) where the confinement of carriers yields locally a larger energy gap. Emission from these regions is responsible for the observed 3 visible emission band.
EXPERIMENTAL DETAILS Hydrogen was inserted by using low-energy ion implantation. The experimental set-up for the implantation has been already described before. 3 -5 Here it suffices to say that (100) Si samples were implanted at 77 K with an H atomic energy of 15.5 keV and with various fluences (b. The implantation conditions were chosen to produce a damage essentially due to Frenkel pairs. Annealing treatments were performed by placing the samples in a furnace in vacuum for the selected times and temperatures (T). The implanted ion specie (H, D, He and 0), the doping type (n and p) or level (from 10-2 Qcm to 104 Qcm), D (1014 - 1017 cm- 2 ), T (100 - 8000 C), annealing duration (30 min to 16 h) and the substrate type (Floating zone and Czochralski) were changed. The samples were characterised by a variety of techniques. In this paper we concentrate on low temperature photoluminescence (see Ref. 2 for details), channelling Rutheford 157
Mat. Res. Soc. Symp. Proc. Vol. 358 01995 Materials Research Society
unimplanted n-T T=6500C
c/i
n-Si0-implanted annealed 450x2 'C
x2
" ,;.
.•T
z
annale 40 Ol0.C,:. p-SiH-implanted
09
WU
annealed 400 C
L
z w
.
LU x2
z. WIp-Si
T =400 OC,' OC A
x10-/ T =2500C
z
w
He-implanted
U) Z
z_ w u
•:.
=500 °C
annealed 450 'C in H2
'l)
__
Z
X1
T= 150 C
p-Si 0-implanted neld800 'C.,
as implanted
06
0.8 1.0 1.2 1.4 WAVELENGTH (pm)
1.6
0.6
Figure 1. 80 K photoluminescence spectra of several implanted and annealed samples. The dotted lines refer to the as-implanted while the full line to the annealed samples.
0.8
1.0 1.2 1.4 WAVELENGTH (gm)
1-6
Figure 2. 80 K photoluminescence spectra of H-implanted p-type Si as a function of the annealing temperature (indicated on each spectrum).
backscattering spectrometry (RBS), 4 elastic recoil detection analysis (ERDA), 3 and deep level transient spectroscopy (DLTS).5
PHOTOLUMINESCENCE AND DAMAGE VS ANNEALING TEMPERATURE In Fig. 1 a summary of the PL spe
Data Loading...
