Glossary entry

Characteristic temperature (T₀)

An empirical parameter quantifying the temperature dependence of a semiconductor laser's threshold current. Larger T₀ corresponds to weaker temperature sensitivity.

The characteristic temperature $T_0$ is defined by the empirical relationship

I_\text{th}(T) \;=\; I_0 \, \exp\!\left(\frac{T}{T_0}\right),

where $I_\text{th}(T)$ is the threshold current at active-region temperature $T$ and $I_0$ is a temperature-independent constant with units of current.

Typical values by material system:

System	Wavelength	$T_0$
AlGaAs / GaAs	750–850 nm	120–160 K
InGaAs / GaAs	900–1100 nm	100–140 K
InGaAsP / InP	1300–1550 nm	50–70 K
InGaAlAs / InP	1300–1550 nm	70–90 K
GaN / InGaN	405–470 nm	90–150 K

Extraction from temperature-dependent LIV data is covered in Characteristic Temperature Extraction from LIV Measurements.