Defect Emission And Heat Radiation Of 450nm GaN-based Semiconductor Laser

Semiconductor lasers have the advantages of high electrical-optical conversion efficiency,long service life,small size,low cost,etc.,and they are widely applied in defense military,medical treatment,pump sources and optical storage.From the point of view of working wavebands,they can be divided into gallium arsenide(Ga As)-based semiconductor lasers and gallium nitride(GaN)-based semiconductor lasers.Although the conversion efficiency of them can be as high as 75%,the remaining unconverted energy will accumulate in the device in the form of heat,causing the degradation and even the irreversible catastrophic optical damage(COD)of the devices and thereby limiting the maximum power output of the lasers.The thesis focuses on GaN-based(In GaN/GaN multiple quantum well structure)semiconductor lasers.With the help of Fourier Transform Infrared(FTIR)spectrometers,the emission of the devices is investigated at different temperatures and different wavelength bands,to explore the defect states and the potential thermal effect in the devices.Following is the achievements of the research:1)In the visible waveband,in addition to the emission signal of the quantum well layer at 450 nm,the lasers also have a strong yellow emission band(about 570-600 nm).The emission signal comes from the defect emission related to the GaN matrix in the active region of the devices.2)In the near-infrared waveband,the emission signals of multiple emission frequency bands were observed,including emission signals in the range of 780-840 nm,900-1100 nm,1200-1320 nm and 1480-1620 nm.Among them,the visible and near-infrared 780-840 nm emission signal may originate from the laser-induced optical radiation accompanying peaks after stimulated emission takes place in the laser.The short-wave infrared 900-1100 nm and 1200-1320 nm emission signals originate from the defect emission in the substrate,while the 1480-1620 nm emission signal comes from the defect emission or the thermal radiation signal in the active region of the devices.3)In the mid-infrared waveband,the devices have a wide emission band at 4-12 ?m.By means of mathematical processing,this signal is derived from the combined contribution of the deep-level defect emission signal within the lasers and the thermal effect of the devices.When the current is lower than 0.5 A,this radiation signal should be derived from the deep-level defect emission signal in the laser material;when the current is elevated beyond 0.5 A,the radiation signal in this waveband is mainly due to the current-induced thermal effect of the devices.