Hole transport due to shallow acceptors along boron doped SiGe quantum wells

Stimulated THz Emission of Strained p-Ge and SiGe/Si Quantum-Well Structures Doped with Shallow Acceptors.

“…15) in comparison with that for p-Ge. On the other hand, the Fermi level is near QW valence band edge and the free hole concentration at equilibrium conditions is of the order of the acceptor concentration in the QW [33,35]. That is why the population inversion would be difficult to get even if impact ionization could occur.…”

Carrier injection as a cause of THz lasing excitation in SiGe/Si QW structures

“…Calculations showed that this energy is about 27 meV [3,4]. On the other hand, the Fermi level is close to the QW valence band edge and the free hole concentration at equilibrium conditions is of the order of the acceptor concentration in the QW [5,6]. That is why the population inversion should be difficult to reach even if impact ionization could occur.…”

Mechanism of terahertz lasing in SiGe/Si quantum wells

“…9 Because the carriers in a SiGe/Si QW are electrically pumped, electric transport in the well has been investigated in detail in order to clarify the relevant physical processes. 8,10 Under a weak dc bias, the temperature behavior of the conductivity , plotted as ln() as a function of the inverse temperature 1/T, exhibits two different linear regimes, below and above TӍ20 K, respectively, as shown by Fig. 1 in Ref.…”

“…8. Further experiments on magnetoconductivity and Hall mobility 8,10 have indicated that the low temperature conductivity may be due to hopping. In the high temperature region, the slope of the ln() vs 1/T curve suggests an activation energy of about 12 meV for Ge content xϭ0.1 and 18 meV for xϭ0.…”

“…13 This charge redistribution inside the sample builds up a strong electric field in the QW, which was detected experimentally. 8,10 Our calculated energy level structure in the QW is shown in Fig. 1.…”