Germanium for VCSEL Applications

Main characteristics of Germanium for VCSELs

No dislocations

Umicore Germanium has 0 EPD (etch pitch density), which results in a better yield and long term device reliability. The burn-in of final devices may be reduced.

Germanium compared to Silicon and GaAs





Crystal Structure Diamond Zincblende Diamond Si and Ge are elemental semiconductors with similar large (12") diameter 0 EPD* cyrstal processes
Density (g/cm³) 2.33 5.32 5.33
Lattice constant (Å) 5.430 5.653 5.658 Ge and GaAs are lattice matched
Bandgap energy at 300K (eV) 1.12 1.42 0.66
Electron mobility (cm²/V-s) 1350 8500 3900 Ge has both high electron and hole mobility
Hole mobility (cm²/V-s) 480 400 1900
Melting point (°C) 1415 1238 937
Thermal expansion (1/°C) 2.6 10-6 5.7 10-6 5.9 10-6 Ge and GaAs have similar thermal expansion
Thermal conductivity (W/cm°C) 1.3 0.55 0.55
Fracture thoughness (MPa.m1/2) 0.8 0.31 0.66 - 0.72 Ge is twice as tough as GaAs

* EPD: Etch pitch density, dislocation density


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