Electrical characterisation of p-doped distributed Bragg reflectors in electrically pumped GaInNAs VCSOAs for 1.3μm operation

Abstract

► We electrically characterised two p -type doped DBRs for 1.3 μm VCSOA applications. ► Abrupt and graded structures were designed and investigated. ► Longitudinal and vertical transports were measured as function of temperature. ► Low series resistivity achieved using the interface composition grading technique. ► Theoretical model confirmed the obtained results. The high resistivity that is encountered in p -type DBRs is an important problem in vertical cavity surface emitting lasers and optical amplifiers (VCSELs and VCSOAs). This is because the formation of potential barriers at the interfaces between layers of high and low refractive index inhibits the carrier flow, thus increasing the DBR series resistance. In this work, the electrical characteristics of two p -type doped DBR structures grown on undoped and p -type doped GaAs substrates have been investigated. The DBRs are designed for VCSOAs operating at 1.3 μm and consist of 14-periods of alternating GaAs and Al 0.9 Ga 0.1 As in the first sample and 14-periods of GaAs and Al 0.3 Ga 0.7 As/Al 0.9 Ga 0.1 As in the second one. For the longitudinal transport sample, Hall mobility and sheet carrier density were measured in the temperature range from 77 to 300 K. In the vertical transport sample, current–voltage ( I – V ) measurements across the DBR layers were carried out at different temperatures in the range between 15 and 300 K. We achieved resistivity reduction in our samples by using an interface composition grading technique aimed at improving the VCSOA characteristics.