Electroluminescence of Yb-Doped InP
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Mat. Res. Soc. Symp. Proc. Vol. 358 0 1995 Materials Research Society
of Yb luminescence is discussed on the basis of quenching mechanisms involving Yb and iron (Fe) proposed by Lozykowski et al. [I].
SAMPLE AND MEASUREMENT Ytterbium ions were implanted into n-type InP ( with electron concentration, n=3.6 x 10" cm 3 at 77 K ) at 145 keV to a dose of I x 10i ion/cm2 . The simulated depth profile, calculated by the Pearson distribution, has the projected range for Yb at 40 nra from the surface, and a Ybconcentration of 2.4x 10"' cm-3 . The samples were annealed at 650 0C for 10 minutes with a rapid thermal annealer with a forming gas ambient. A semi-transparent gold layer ( 100 A thick) was deposited on the implanted surface of the 0.5 mm thick InP sample. A second indium contact was made at the back side of the sample as shown in the schematic of the inset of Fig. 1. The sample holder was mounted on a cold finger cooled by a closed-cycle helium cryostat down to 9 K. The intensity and current versus voltage characteristics and the electroluminescence (EL) measurements -were carried out using a Keithley 236 Source Measure Unit. The EL intensity and current versus voltage characteristics were measured by applying a linear "staircase" voltage waveform in which the voltage signal was changed in steps of 0.015 V from 0 V to 3 V with a time delay of one second at each step. The current and emission intensity were measured at the end of the delay of each step. For comparison, the photoluminescence spectra were also measured for the same sample with the Ar+ 488 nm laser as an excitation source. The emission was dispersed by a Jarrel Ash model 78-490, 0.75 M, scanning monochromator equipped with a 1180 grooves/mm grating. The detection electronics consists of a thermoelectrically cooled Hamamatsu R632-01 photomultiplier with spectral response extended to the IR region. The signals from the photomultiplier passed through a fast preamplifier to a dual channel gated photon counting system controlled by a computer, which also controlled the scanning monochromator. The electroluminescence kinetics (rise and decay) were measured using an HP8013B pulse generator and the Turbo-Multi Channel Scaler (Turbo-MCS, EG&G Ortec) photon counting system that offers a wide range of channel dwell times (minimum 5 ns), with no dead time between channels. All the spectra and kinetics data were stored in the computer for further processing.
RESULTS AND DISCUSSION 1.2
The electroluminescence spectra of InP:Yb at 9 K consist of one sharp peak at 1001 nm EL: AppliedVoltage 2.76V InP:Yb 10 InP:Yb
1.0
PL: Excitation Power 60 mW (Ar laser - 48s nm)
Current 16.8 miA
Temp. 9 K
AuLayer
10.2. Temp. 9K
InP:Yb
-• 10-3.
.L 0.S
47i0.8 0,
.0-
EL
0.6 mnA--j
10-4.
"Q10 0.4
1..
~10.6
-0.2-
0.0
995
1.7 V
10",,
1012
1000
1005 1010 1015 Wavelength (nm) Fig. 1 Comparison of the electroluminescence and photoluminescence spectra of InP:Yb. Inset shows schematic structure of InP:Yb
10
10
Voltage (volts)
101
Fig. 2 I-V Characteristics for
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