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Investigation of thermal properties of mid-infrared AlGaAs/GaAs quantum cascade lasers
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10.1063/1.4746791
/content/aip/journal/jap/112/4/10.1063/1.4746791
http://aip.metastore.ingenta.com/content/aip/journal/jap/112/4/10.1063/1.4746791

Figures

Image of FIG. 1.
FIG. 1.

Structure geometry of a typical QCL, mounted epi-layer down, used in the 2D model. Calculations were performed on nonuniform computational mesh.

Image of FIG. 2.
FIG. 2.

Temperature distribution map (scanned area 40 μm × 80 μm) measured for supply current I = 300 mA, constant frequency f = 840 Hz, and pulse width τ = 100 μs (a) and 500 μs (b). Temperature line scans for different pulse widths at constant frequency f = 840 Hz and supply current I = 300 mA (c). The inset shows SEM photograph of examined structure.

Image of FIG. 3.
FIG. 3.

Temperature distribution map (scanned area 55 μm × 80 μm) measured for a device operated at 240 μs pulse width at frequency f = 840 Hz and supply current I = 300 mA (a) and I = 1000 mA (b). Temperature line scans for different supply current at constant frequency f = 840 Hz and pulse width τ = 240 μs (c).

Image of FIG. 4.
FIG. 4.

Comparison of experimental (a) and calculated (b) temperature distribution maps on the facet of the laser. Temperature line scans at the centre of the AR (c).

Image of FIG. 5.
FIG. 5.

Temperature maps calculated assuming bulk thermal conductivity of the active region (a) and for thermal conductivity in the growth direction reduced by the factor of 10 (b).

Image of FIG. 6.
FIG. 6.

Temperature line scans (a) and maximal temperature increases (b) extracted from maps calculated for different values of AR thermal conductivity in the growth direction.

Image of FIG. 7.
FIG. 7.

Calculated temperature distribution maps for solder thermal conductivity of: κ = 57 W/K·m (a), κ = 2 W/K·m (b), and κ = 0.2 W/K·m (c).

Image of FIG. 8.
FIG. 8.

Calculated vertical line scans for different solder thermal conductivity, ranging from κ = 57 W/K·m to κ = 0.2 W/K·m (a), temperature increases versus solder thermal conductivity (b) and comparison of calculated vertical line scans for different solder thermal conductivity with experimental results measured for two QC lasers (c).

Image of FIG. 9.
FIG. 9.

Calculated temperature distribution maps for properly aligned laser (0 μm offset over the edge of the copper mount). Maximal temperature increase is localized in the active area and reaches the value of ΔT = 14 K.

Image of FIG. 10.
FIG. 10.

Calculated temperature distribution maps for a misaligned laser (10 μm offset over the edge of the copper mount). Maximal temperature increase is localized in the active area and reaches the value of ΔT = 20 K.

Image of FIG. 11.
FIG. 11.

Calculated temperature distribution maps for a misaligned laser (20 μm offset over the edge of the copper mount). Maximal temperature increase is localized in the active area and reaches the value of ΔT = 24 K.

Image of FIG. 12.
FIG. 12.

Calculated temperature profile along the laser cavity.

Image of FIG. 13.
FIG. 13.

Comparison of measured temperature profiles for series I and series II devices, black dashed line corresponds to series I QCL operated with pulse width τ = 10 μs, I = 2 A, dc = 1%, grey dashed line corresponds to series II QCL operated with τ = 10 μs, I = 2 A, dc = 0.1%, black solid line refers to calculated temperature profile.

Image of FIG. 14.
FIG. 14.

Light-current-voltage (L-I-V) characteristics in the temperature range from 77 K to RT for: 15 μm × 1 mm mesa (a), 25 μm × 2 mm mesa (b), and 35 μm × 1 mm mesa (c).

Image of FIG. 15.
FIG. 15.

Threshold current density versus temperature for different mesa dimensions; fitted lines calculated according to the formula .

Image of FIG. 16.
FIG. 16.

Temperature distribution maps (scanned area 80 μm × 115 μm) measured for pulse width τ = 10 μs (a) and τ = 50 μs (b) at constant frequency f = 1 kHz and supply current I = 2.24 A. Temperature line scans for different pulse width at constant frequency (c). The inset shows maximum temperature change versus pulse width.

Image of FIG. 17.
FIG. 17.

Temperature distribution maps (scanned area 80 μm × 115 μm) measured for frequency f = 1 kHz (a) and f = 3 kHz (b) at constant pulse width τ = 10 μs and supply current I = 2.24 A. Temperature line scans for different frequency at constant pulse width (c). The inset shows maximum temperature change versus frequency.

Image of FIG. 18.
FIG. 18.

Temperature distribution maps (scanned area 80 μm × 115 μm) measured for supply current I = 2.24 A (a) and I = 3.4 A (b), pulse width τ = 10 μs, and frequency f = 1 kHz. Temperature line scans for different supply currents (c). Inset shows maximal temperature change versus supply current.

Image of FIG. 19.
FIG. 19.

Active region temperature rise versus electrical power (a) and current density (b) for QCLs with different mesa dimensions.

Tables

Generic image for table
Table I.

Thermal conductivities and layer thicknesses used in simulations.

Generic image for table
Table II.

Comparison of parameters extracted from measurements of series II QCLs with different mesa dimensions.

Generic image for table
Table III.

Comparison of parameters extracted from measurements for QCLs differing in the mesa dimensions for series I and series II lasers.

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/content/aip/journal/jap/112/4/10.1063/1.4746791
2012-08-31
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Investigation of thermal properties of mid-infrared AlGaAs/GaAs quantum cascade lasers
http://aip.metastore.ingenta.com/content/aip/journal/jap/112/4/10.1063/1.4746791
10.1063/1.4746791
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