| The avalanche photodiode?APD?detectors with high detection rate,high sensitivity and intelligent integration are widely used in modern communication systems because of the demand of the low noise and high signal to noise ratio detectors for fiber transmission and quantum communication technology.The researches of the separate,absorption,grading,charge and multiplication?SAGCM?In Ga As/InP APDs have been done.Firstly,the influences of the InP charge layer and bias voltage on the distribution of the electric field of the In0.53Ga0.47As/InP SAGCM-APD detector were studied by using the silvaco-TCAD simulation software.The effects of the InP charge layer and InP multiplication layer on the punch-through voltage and the breakdown voltage were investigated.In addition,the characteristics of the small signal and the characteristics of the light response of the In0.53Ga0.47As/InP SAGCM-APD detector were studied.The electric field of the In0.53Ga0.47As/InP SAGCM-APD detector increases with increasing the reverse bias voltage.With the increase in charge density of the InP charge layer,the electric field of the InP multiplication layer increases,while as the In Ga As absorption layer electric field decreases.The punch-through voltage of the device is linearly increased and the breakdown voltage is linearly decreased by increasing the charge density of the InP charge layer.When the charge density of the InP charge layer is bigger than a certain value,the breakdown voltage of the APD device firstly decreases and then increases with increasing thickness Wm of the InP multiplication layer.At 0.4 ?m,the breakdown voltage has a minimum value Vbmin of 29 V,and the punch-through voltage increases linearly with increasing thickness of the InP multiplication layer.Further,when the thickness of the InP charge layer is relatively small,the punch-through voltage has a fixed value and the breakdown voltage decreases with the increase in the doping concentration of the InP charge layer.The capacitance increases with decreasing the reverse bias voltage,and the capacitance decreases with the increase in the thickness of the multiplication layer.The capacitance density is about 4.5×10-17 F/?m when the thickness of the InP multiplication layer is 1 ?m,the reverse bias voltage is-5 V and the frequency is 1 MHz.The responsivity of the APD detector is 1 A/W and 1.1 A/W at the wavelength of 1.31 ?m and 1.55 ?m,respectively.Secondly,the In0.53Ga0.47As/InP SAGCM-APDs with low dark current and wide response range have been prepared by molecular beam epitaxy and open-tube zinc diffusion method.At 600 ?,by Zn diffusing for 13 min,16 min and 17 min,the corresponding thickness of the InP multiplication layer is 1.5 ?m,1 ?m and 0.83 ?m,respectively.The dark current is less than 10 n A at 0.95Vb?Vb is the avalanche breakdown voltage?,and the multiplier factor M is increased to 20?linear model?,and the capacitance density is as low as 1.43×10-8 F/cm2 when the bias voltage is-5 V.The response range of the APD detector is from 50 n W to 20 m W,and the responsibility of the APD detector is up to 1.13 A/W under the radiation of 1310 nm infrared laser at 30 V reverse bias voltage.The punch-through voltage and breakdown voltage were studied by changing thickness of the InP multiplication layer and doping concentration of the InP charge layer.The results show that the punch-through voltage increases linearly,on the contrary,the breakdown voltage decreases linearly with the increase in the charge surface density of the InP charge layer.Further,the breakdown voltage increases and punch-through voltage also linearly increases with increasing thickness of the InP multiplication layer when the charge surface density of the InP charge layer is 4.8×1012 cm-2.By optimizing device structure,growth parameters and process techniques,the In0.53Ga0.47As/InP SAGCM-APD with a low dark current and wide response range has been obtained. |
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