Carrier loss channels for non-collected carrier in InAsxP1−x∕InP multiquantum well solar cells

Abstract

We present here the direct observation of majority carrier (electron) defects generation from chemical-beam epitaxy grown InAsxP1−x∕InP multiquantum-well solar cell structures by deep level transient spectroscopy. Four dominant majority carrier levels E1, E2, E3, and E4 at energy position EC−0.17eV, EC−0.25eV, EC−0.57eV, and EC−0.75eV below the conduction-band edge have been observed. Detailed analysis of double-correlation deep level transient spectroscopy (DDLTS) measurements shows that traps E1, E2, E2, and E4 are located at the well-barrier interfacial zone or/and extended over the whole region occupied by the quantum wells. The midgap center E3 has large capture cross sections and is found to exhibit significant dependence of the thermal emission rates on electric field, from DDLTS measurements. These characteristics indicate that the electron trap E3 at EC−0.57eV acts as a strong recombination center and could be responsible for the main carrier loss channel for non-collected carrier in the device.