Low Temperature Grown Thin Inalas Step Graded Buffers for Application on Optical Modulator at 1.3 μM

Abstract

ABSTRACTPreliminary results are described about the growth, structure and properties of multiple quantum well(MQW) Quantum Confined Stark Effect (QCSE) modulators grown on GaAs substrates for operation at 1.3μm in wavelength. Step graded InAlAs buffer layers grown at low temperature by molecular beam epitaxy (MBE) with a total thickness of 0.3 μm are used to relieve the strain caused by the lattice-mismatch between the GaAs substrate and the In0.35Ga0.65As/In0.35Al0.65As MQW heterostructure. X-ray diffraction spectra show that significant lattice relaxation takes place in the buffer. A quantum confined Stark shift of the exciton absorption peak of 48meV was obtained with an applied electric field of 130KV/cm, measured in PIN diode structures consisting of 30 period 95ÅIn0.35Ga0.65As/100ÅIn0.35Al0.65As MQWs on a 3 stage compositionally step graded InxAl1−xAs buffer doped with Si to 5*1017/cm3 grown on a nominally 1018/cm3 n-type doped GaAs substrate.