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It has been theoretically predicted that 1.4%biaxial tensile strain can convert Ge,which is compatible with Si CMOS technology,into a direct band-gap semiconductor [1] and increase the carrier mobility dramatically.The excellent electronic and optical properties of the tensile-strained Ge make it a candidate material for both electronic and optoelectronic devices integrated on Si [2-4].We grew the tensile-strained Ge quantum dots(TSGeQD)on InP successfully by MBE and proved that there was direct band-gap part in them by strain analysis,making the TSGeQD one of the most promising candidates to construct light sources for Si-photonics integration [5].In this work,we choose In0.52Al0.48As as the barrier layer to confine electrons and holes in order to enhance recombination.As a result,we achieved photoluminescence(PL)from TSGeQDs and demonstrated experimentally that the TSGeQD is a promising light emission material.The sizes of most QDs were uniform with the diameter around 40 nm and the height around 8 nm.As shown in Fig.1(a),most strain was held in the QD and the strain was larger than the threshold of indirect-to-direct band gap conversion.Fig.1(b)is the PL spectra of the tensile-strained Ge QDs whose peak value of the wavelength is 1250 nm at room temperature.The emission is proved to come from TSGeQD layer by etching experiments.The PL intensity from the TSGeQD is stronger than that from InP for two orders of magnitude,which is a strong evidence that the emission is from direct band gap.