Characterization of Double-Junction GaAsP Two-Color LED Structure

The structural, optical, electrical and electrical–optical properties of a double-junction GaAsP light-emitting diode (LED) structure grown on a GaP (100) substrate by using a molecular beam epitaxy technique were investigated. The p – n junction layers of GaAs 1− x P x and GaAs 1− y P y , which form the double-junction LED structure, were grown with two different P/As ratios. High-resolution x-ray diffraction (HRXRD), photoluminescence (PL), and current–voltage ( I – V ) measurements were used to investigate the structural, optical and electrical properties of the sample. Alloy composition values ( x , y ) and some crystal structure parameters were determined using HRXRD measurements. The phosphorus compositions of the first and second junctions were found to be 63.120% and 82.040%, respectively. Using PL emission peak positions at room temperature, the band gap energies ( E g ) of the first and second junctions were found to be 1.867 eV and 2.098 eV, respectively. In addition, the alloy compositions were calculated by Vegard’s law using PL measurements. The turn-on voltage ( V on ) and series resistance ( R s ) of the device were obtained from the I – V measurements to be 4.548 V and 119 Ω, respectively. It was observed that the LED device emitted in the red (664.020 nm) and yellow (591.325 nm) color regions.