窄台衬底内条形半导体激光器

研制了一种新型结构双异质结半导体激光器,这种激光器是利用非平面衬底液相外延的特点,使电流阻挡层和四层双异质结构在腐蚀成窄台的衬底上一次外延完成生长,内条形电流通路在外延生长中自然形成.工艺特别简单,且具有良好线性输出和稳定基横模式振荡等特点.

NARROW MESA SUBSTRATE INNER STRIPE SEMICONDUCTOR LASER

In seeking for semiconductor lasers with simple fabrication process and good performance,plenty of lager structures has been developed to realize the current confinement in lateral direction.As an effective way for this purpose,it was considered to form a current blocking layer inside the heterostructure and then allow the current to flow within a narrow path,as in the case of VSIS laser.In VSIS laser,two-Step epitaxial growth and photolithography and V-groovc etching on the epitaxial wafer are inevitable.Recently,we designed a laser with new structure,the terraced substrate inner stripe laser(TSIS).The TSIS laser has a simple fabrication process.It is fabricated by one-step liquid phase epitaxy without mask deposition and Zn diffusion.However,this TSIS laser needs a precise control of melt saturation and growth time of the current confinement layer.To make the laser fabrication process even simpler,a new structure laser with a narrow mesa substrate is developed(Fig.1).This new narrow mesa substrate inner stripe laser(NMSIS)is fabricated by simillar techniques to TSIS laser,using one-step liquid phase epitaxy without mask deposition and Zn diffusion.After a narrow trapezoidal mesa is etched on the substrate,making use of the properties of liquid phase epitaxy over a non-planar substrate,the growth of all layers including GaAlAs current confinement layer is accomplished by one-step liquid phase epitaxy.In growing the current confinement layer(first one),because the growth melt is effectively undersatu-rated for convex areas and the lateral diffusion is induced by local Solute concentration gradient between convex areas and concave ones,the shoulder of the mesa is melt-etched,the region on the mesa is just saturated,and at the same time the epitaxy layer is formed on the areas beyond the mesa part.By using this technique of crystal growth,the inner stripe for current channel is as narrow as 3 to 5um on the meSa.The confinement layer could be contiolled as thick as desirable.It''s over 1μm in our experiment,which is enough to prevent the current leakage outside current channel.Apart from the very simple fabrication process of this structure,there are some other advantages.The spontaneous absorption in confinement layer instead of GaAs is reduced.Primarily,the lasers stimulate with threshold current of 80~120mA and the wavelength of 7800-8100Å.Since the NMSIS laser is narrow gain guide,the laser has linear power veisus current characteristics and fundamental mode operation with up to 3-4 times threshold current and over 25mW maxium power output.The relation of field distribution to the current path width has been studied.The far field patterns in single,double and triple peaks in fundamental lateral mode are found in different cunent channel width.