Gain Comparison For Periodically Delta-Doped P-Ge Structures With Vertical And In-Plane Transport

Calculated terahertz gain for periodically delta-doped p-Ge films with vertical and in-plane transport and an orthogonal magnetic field are compared. Gain as a function of structure period, doping concentration, field strength, and temperature is calculated using distributions determined from Monte Carlo simulations. Both transport schemes achieve spatial separation of light holes from impurity layers and the majority of heavy holes, which significantly increases light hole lifetime and gain compared with bulk p-Ge lasers. For in-plane transport, an optimum doping period of 1 - 2 μm and a 10-fold increase in gain over bulk p-Ge are found. For vertical transport, the optimum period is 300 - 400 nm, and the gain increase found of 3 - 5 times bulk values is more modest. However, it is found that gain can persist to higher temperatures (up to 77 K) for vertical transport, while the in-plane transport scheme appears limited to 30 - 40 K