Light-Emitting Si:Er:O Diodes Operating In The Avalanche Regime
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ABSTRACT Electroluminescence (EL) characteristics of avalanching diodes fabricated by Er and 0 co-implantation and subsequent annealing have been studied. Distribution of Er 3+-related EL at 1.538 ý.tm was found to be uniform over the device area at 300 K. Saturation of the Er-related EL intensity is achieved under the avalanche regime at current density one order of magnitude lower than that under the tunnel regime. An EL decay is less than 10 .ts (being time response of our detector) after the diode turned off the avalanche regime. INTRODUCTION An increased interest to investigation of erbium-doped single crystal silicon is associated with its possible application in optoelectronics. This system shows temperature-independent luminescence at the wavelength of- 1.54 .tm due to internal-4f shell transitions between the first excited level (4113/2) and the ground state (4115/2) of the Er 3÷ ions. EL under forward bias [1] and reverse bias in the tunnel breakdown regime [2] was observed at room temperature for the first time in 1991 and 1994, respectively. A reduced temperature quenching of the EL intensity at reverse bias as compared with that of forward bias is usually associated with a difference in the excitation mechanisms: an indirect carrier-mediated process at forward bias and impact ionization by hot carriers at reverse bias [3]. Recently, we have observed room temperature Errelated EL at the avalanche breakdown regime [4]. In this paper EL characteristics of avalanching diodes have been studied. EXPERIMENT The starting wafers of phosphorus-doped and Cz silicon (5-20 Q cm) were used as substrates. To increase the Er-related luminescence intensity, we used a conventional procedure of erbium and oxygen ion co-implantation [2-4]. Erbium ions were implanted at two energies of 2.0 and 1.6 MeV and doses of lxlO14 (samples #1) and lxlO13 cm 2 (samples #2). Oxygen co-implantation with two energies 0.28 and 0.22 MeV and doses of lxl015 (samples #1) and IxI10 4 cm 2 (samples #2) was designed to specially overlap the erbium implant. According to SIMS measurements, maximum concentrations were equal to 4.6x 1018 Er/cm-3, 4.3x 10"7 Er/cm-3 , 5.0x 1019 O/cm"3 , and 4.9xl 018 O/cm" 3, respectively. Rutherford back scattering of protons with an energy of 234 keV has shown that the erbium and oxygen co-implantation with lower doses did not lead to amorphyzation of implanted layers. To anneal implantation damage and activate optical sites, annealing at 9000 C for 0.5 h in a chlorine-containing atmosphere was used. The chlorine-containing atmosphere was an oxygen flow with addition of thrichloroethylene with a concentration of 0.5 mole % [4]. In contrast, co-implantation with higher doses (samples #1) produced a continuous amorphous near-surface layer. In this case, heat treatment of 6200 C/1 h + 139 Mat. Res. Soc. Symp. Proc. Vol. 486 01998 Materials Research Society
9000 C/0.5 h in the chlorine-containing atmosphere was carried out. The annealing at 6200 C induces the solid phase epitaxial recrystallization of this layer. Fu
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