| Popis: |
The doping superlattice1 consists of thin alternating layers of n- and p-doped semiconducting material. The electric field induced by carrier migration leads to band bending and to an indirect band gap in real space. The energy of this indirect band gap can be tuned by creating electron–hole pairs by means of laser excitation, thus changing the transmission, reflection, and photoluminescent properties of the superlattice. GaAs doping superlattices having various layer thicknesses and dopant levels were grown by means of molecular beam epitaxy. Optical properties of the samples were measured at temperatures ~300, 80, and 5 K. Modulation of the optical properties by an exciting Ar laser was strongest at 5 K and too small to be observed at 300 K. At 5 K, under appropriate laser excitation, photoluminescent peaks were shifted toward longer wavelengths, as far as 9300 Å. Laser-modulated absorption was observed from 8250 Å, corresponding to an energy slightly less than the GaAs direct band gap, to 8900 Å. The experimental results are compared with theoretical calculations of properties of doping superlattices. |
