Ga(In)SbBi alloys for mid-IR applications: growth and characterization O. Delorme, L. Cerutti, E. Tournié and J.-B. Rodriguez* IES, Univ. Montpellier, CNRS, 34000 Montpellier, France *Corresponding author:
[email protected] Work partly supported by ANR under project BIOMAN (ANR-15-CE24-0001) and by the French "Investment for the Future" program (EquipEx EXTRA, ANR-11-EQPX-0016)
Context
Objectives
III-V-Bi alloys exhibit interesting properties: Rapid bandgap reduction with %Bi Increased spin-orbit splitting energy
Study of Bi incorporation
Bi flux
GaSb GaSbBi
-8
Bi BEP 4.5x10 Torr
Bi content (%)
Bi content (%)
5
-8
Bi BEP 3.5x10 Torr 6
4
Bi BEP 2.3x10-8 Torr
4
ratio Ga/Sb ~1 3
Wavelength (µm) 6
Intensity (arb. u.)
GaSb1-xBix
3.8%
0
GaSbBi 8.4% 11.4%
250
300
29.8
350
2.6
2.8
3.0
3.2
3.4
3.6
Optimized growth temperature: 200°C (Thermocouple temp. reading) Excellent control of the Sb/Bi flux required
GaSbBi/GaSb QWs 300K
7 / 11 / 15 nm-Ga(In)SbBi/20 nm-GaSb 3 x QWs 180 nm GaSb 20 nm AlAs0.08Sb0.92 barrier
30.4
30.6
Chemically sensitive g002 DFTEM images of the GaSb0.89Bi0.11/GaSb QWs (E. Luna, PDI, Berlin)
~15 nm, 11% Bi 2.63 µm
x10
~7 nm, ~15% Bi ~2.95 µm
x10
2.0
0.2
0.3
0.4
0.5
0.6
3.0
3.5
0.8
0.9
PL measurements at RT for GaSbBi alloys
300K
Ws bQ
/
GaS
/
s QW b S Ga
n .037 GaI 0
i .07 SbB 0
In 0.037
Ga
/ 5
s QW b GaS
Ga0.963In0.037SbBi/GaSb QWs
6% Bi 2.20 µm
7% Bi
i 0.10
SbB
2.34 µm
In 0.037
Ga
10.5% Bi 2.56 µm
~3.30 µm
2.5
0.7
Energy (eV)
4.0
29.6
29.8
30.0
30.2
30.4
30.6
30.8
2.0
31.0
PL measurements at RT of GaSbBi/GaSb MQW with various thicknesses and Bi concentrations
2.5
3.0
3.5
PL emission wavelength (µm)
PL emission wavelength (µm)
Ga(In)SbBi/GaSb MQW structure
(x2)
3.8 µm
i .06 SbB 0
2.48 µm
GaSb:Te substrate
11.4%
Droplet free samples for Bi content < 12% Excellent crystal quality with Bi content as high as 14% PL emission at room temperature (RT) demonstrated up to 3.8 µm
~11 nm, 11% Bi
~11 nm, ~15% Bi
2.2 µm
30.8
HR-XRD scans of GaSbBi films for different Bi contents. The Sb flux was adjusted to maintain a stoichiometric V/III ratio.
2.10 µm
100 nm GaSb buffer
6.2%
14%
~15 nm, 6% Bi
PL intensity (arb. u.)
200°C (TTR)
30.2
Ga(In)SbBi/GaSb QWs
20 nm GaSb
180 nm GaSb
2 µm
Bi content in GaSb1-xBix alloys as a function of Sb beam equivalent pressure (BEP) at a fixed Bi flux
20 nm AlAs0.08Sb0.92 barrier
30.0
3.8
Sb BEP (x10-7 Torr)
Thermocouple temperature reading (TTR) (°C)
Bi content in GaSb1-xBix alloys as a function of growth temperature with different Bi beam equivalent pressures (BEP) for each set of samples. The Sb flux was adjusted to maintain a stoichiometric V/III ratio.
4.0%
2.8 µm
Intensity (arb. u.)
200
2
GaSb
PL intensity (arb. u.)
0 150
3
6.2%
14.0% 1
4
300K
2
2
5
Intensity (arb. u.)
6
8
Sb flux Droplet free surface
12
10
Methods: • MBE (RIBER C21E) • (001) GaSb substrates • RGa ~ 0.3 ML/s
Growth of high Bi-content GaSbBi alloys
Growth temperature and Sb flux are critical parameters for Bi incorporation: GaSb1-xBix
Growth of high Bi-content Ga(In)SbBi alloys by MBE Realization of type-I Ga(In)SbBi/GaSb MQW structures
But the growth is very challenging: Extremely low growth temperatures Stoechiometric V/III ratio
HR-XRD scans and PL emission at RT of 15-nm thick Ga0.963In0.037SbBi/GaSb MQW with different Bi contents
GaSbBi/GaSb QWs PL emission up to 3.3 µm at RT 15 nm-thick GaIn0.037SbBi/GaSb QWs with Bi content up to 10.5% PL emission up to 2.56 µm at RT Bi concentration PL intensity Degradation of the material quality
GaSbBi-based laser
2.50 µm
Normalized intensity (arb. u.)
2.0
GaSb
Intensity (arb. u.)
1.5
GaSbBi
Voltage (V)
300K
1.0
0.5
29.5
30.0
30.5
0
100
GaSb0.885Bi0.115/GaSb MQW laser structure
HR-XRD scan of the laser and its simulation (in red)
80K 200K 260K 300K
2.45
2.50
2.55
2.60
2.65
2.70
Wavelength (µm)
200
300
400
500
600
Current (mA)
Bright-field STEM image of the GaSbBi/GaSb active zone (E. Luna, PDI, Berlin)
2.75
Laser spectra at different temperatures under pulsed operation.
0.0
31.0
pulsed I = 1.1 Ith
I-V and L-I (under pulsed operation) characteristics at RT and 80K.
Simple type-I QWs with a Bi content ~ 11.5% CW lasing at 80K at 2.52 µm with a threshold current density Jth ~ 586 A/cm² Pulsed laser emission at RT at 2.71 µm with Jth ~ 4.22 kA/cm²
CW, I = 1.1 Ith
2.52 µm
80K
Intensity (arb. u.)
GaSb0.885Bi0.115 / GaSb laser
80K
Optical intensity (arb. u.)
Measurement Simulation
2.66 µm 2.71 µm
2.57 µm
CW laser emission at 80K 2.50
2.52
Wavelength (µm)
Summary Successful growth of high-quality GaSbBi alloys with Bi content up to 14% Growth of GaSbBi/GaSb MQW structure emitting up to 3.3 µm at RT Growth of Ga0.963In0.037SbBi/GaSb MQW with Bi concentration up to 10.5% emitting at 2.56 µm (RT) First GaSbBi-based laser: emission at 80K at 2.52 µm in CW mode and at RT at 2.71 µm under pulsed operation
2.54
