The universal behaviour of shallow-deep level instabilities in semiconductors

In Al0.1Ga0.9As:Ge two photoconductivity (PC) effects related to the DX- (p ersistent PC) and A(1) (giant PC) states are studied under hydrostatic pres sure. We found that the barrier for electron capture to the DX- state, resp onsible for the persistent PC, changes its character for p > 10(9) Pa and b ecomes pinned to the conduction band (CB) edge. Another barrier linked with giant PC, responsible for electron capture on A(1) state is pinned to the CB edge for all pressures. A new universal configurational coordinate diagr am of donor related levels including two types of lattice deformation, of C -3v symmetry for DX- and Td symmetry for A(1), is proposed. It describes bo th shallow-deep A(1) and DX- level instabilities and explains e.g. why capt ure of electrons to the DX- state goes via an intermediate effective mass s tate, or why for extremely sharp shallow A(1) state anticrossing behavior i s observed.