InGaAsP MQW electroabsorption modulators with tensile-strained barriers

Abstract

Tensile strain is introduced to the barriers of InGaAsP MQW electroabsorption modulators operating near the transmission-loss minimum for optical fibers. The frequency response and optical saturation of quantum-well modulators depends on the carrier-escape time. Figure 1 illustrates the band structure for 9-nm-wide InGaAsP quantum wells with an unbiased transition wavelength of 1.48 μm and a conduction-band discontinuity of 140 meV.1 For completely-lattice-matched structures, the large valance-band discontinuity and greater mass results in an escape time that is much larger for the heavy hole than for the electron. Compressive strain in the well reduces valance-band offset relative to the conduction-band offset by pushing down the valance-band energy in the well.2 Tensile strain in the barriers reduces the valance-band offset by pushing up the valance-band energy in the barrier.