InP Based Transistor Laser (TL) Structure *S

Transistor laser (TL) is a novel optoelectronic device, which introduces quantum well materials near the base region of traditional bipolar transistors to provide optical gain, and introducing feedback cavities formed by cleavage planes or gratings in the device. TL has both the current control function of transistors and the light emission function of lasers. By using one electrical signal input, it can simultaneously obtain one electrical signal output and one optical signal output, with multiple superior characteristics and important application prospects. The InP based long wavelength TL with emission wavelengths of 1.3um and 1.5um is more suitable for fiber optic communication system applications compared to short wavelength GaAs based devices. PAM-XIAMEN can produce InP based long wavelength transistor laser epitaxial wafer, take the following structure for example:

1. InP Based Transistor Laser Epi-Structure with 1.5um Emission Wavelength

2. About Transistor Laser

According to different structures, ridge waveguides TL mainly include three types: shallow ridge waveguides, buried ridge waveguides, and deep ridge waveguides. The active quantum well material in the shallow ridge transistor laser is placed in the heavily doped base material, making the InP based transistor laser only able to operate at low temperatures. The InP based transistor laser with buried structure adopts npnp type InP current blocking layer buried ridge stripe type active material, and the manufacturing process is too complex, which is not conducive to reducing device costs. The active material of the quantum well in the deep ridge transistor laser is located on top of the heavily doped base material, which can simultaneously reduce the adverse effects of doping impurity diffusion and base material light absorption. Compared to shallow and buried ridge TLs, deep ridge waveguide TL has a simpler fabrication process and less impact of heavily doped base material on the optoelectronic performance of the device.

Fig. 1 is a scanning electron microscope image of the cross-section of an npn type InP based deep ridge transistor laser waveguide. The quantum well material in the device is only in contact with the p-type base material below, effectively reducing the influence of p-type doping impurity Zn diffusion. Comparing the photoluminescence spectra of the same InGaAs quantum well material in deep ridge and shallow ridge TL structures, it can be found that quantum wells in deep ridge transistor laser structures have better luminescence quality, manifested as higher luminescence intensity and smaller spectral width. At the same time, the severe p-type doping impurity Zn towards quantum well material expansion also causes a significant blue shift in the emission wavelength of quantum well materials in shallow ridge devices. In addition to reducing the influence of Zn diffusion, the distribution of light field in heavily doped base materials in deep ridge TL is also reduced, which can reduce the absorption of device luminescence by base materials.

Fig. 1 Cross section SEM image of npn InP based TL

For more information, please contact us email at [email protected] and [email protected].