Research On Theory And Design Of Extended Wavelength Avalanche Photodiodes

Recently,with the increasing attention to the eye safety in lidar system,and the ca-pacity saturation of traditional telecommunication frequency bands,expanding the work-ing wavelength of avalanche photodiodes from the conventional 1.55μm to 2μm window has attracted more and more attention.This paper replaces the absorber layer In Ga As material with Sb-based In_0.53Ga_0.47As/Ga As_0.51Sb_0.49 type-Ⅱsuperlattice on the existing basis of the traditional In Ga As/In P SAGCM APD,the operation wavelength can not only be applied to the communication band of 1.55μm,but also can respond to 2.8μm.A sys-tematic simulation and theoretical analysis were carried out on the parame-ters of each layer of the device structure,and a series of rules were summarized.The de-tailed study content is listed as follows:1.The parameters of In_0.53Ga_0.47As/Ga As_0.51Sb_0.49 superlattices are calculated by lin-ear interpolation method.The energy band of superlattices is calculated by equivalent material method.The relevant parameters such as the band offset,energy band offset,static dielectric constant and Luttinger parameters in the superlattice material model are calculated for further device strucutre simulation.2.Theoretical simulation and analyses of the constructed device structure were per-formed with changing the layer thickness and doping concentration.In this part,the ab-sorption layer,the multiplication layer,the charge layer and the grading layer are ana-lyzed and discussed.The results showed that as the doping concentration of absorption layer increases,the breakdown voltage point increases;As the thickness of the absorp-tion layer increases,the absorption probability of APD increases.When the thickness is3μm,the absorption probability of 2μm wavelength is 45%.The absorption probability of 1.5μm wavelength can reach 80%.When the thickness of the multiplication layer is increased from 0.1μm to 0.6μm,the punch-through voltage increases linearly from 16V to 48V;the breakdown voltage firstly decreases and then increases,and there is a critical point where the thickness of the multiplication layer is 0.35μm.The grading layer in the device structure reduces the hole barrier caused by the valence band shift between the absorption layer and the multiplication layer,and has a adjusting effect on the electric field of the device;Increasing of the doping concentration of the graded layer with1×10¹⁶cm^-3,the breakdown and punch-through voltage points increase by 1V.3.I-V characteristics at different operation temperatures were simulated,and dark current mechanism of the device were analyzed.It is found that the dark current of the device is sensitive to temperature,and the dark current decreases by an order of magni-tude for every decrease of 30°C.After the temperature is lowered,the change of break-down voltage with temperature conforms to the linear function of the traditional In-Ga As/In P SAGCM structure,and the calculated temperature drift coefficient is 0.13V/℃.At the same time,the multiplication gain after cooling is calculated.Under the condition of 240K,the gain has exceeded 100 and the quantum efficiency is as high as 70%.