Study Of The C-V Characteristics On The InP-based Devices

In this paper,the C-V characteristics of In P based devices,such as Ti W/p-In P and In Ga As/In P PIN photodetectors are studied deeply.The method of combining experiment with physical model is used to study.First,the parameters of the epitaxial are designed,such as the thickness doping of each layer,etc.Then,the devices are prepared by semiconductor fabrication process,and the mechanisms of the physical phenomena are analyzed.And then a model is established for quantitative or qualitative analysis combined with the experimental data.Firstly,the C-V characteristics of Ti W/p-In P Schottky contact are studied.It is found that the value of capacitance increases and then decreases with the increased of applied reverse bias voltage,so a peak capacitance appears.The value of the peak capacitance decreases with the increased of frequency.And,the peak position shifts to the left as the frequency increases.Because the effects of interfacial states and series resistors are existed in the device,which will affect the carrier transport in the semiconductor under the influence of the external frequency.Based on the physical mechanism of interfacial state and series resistance effects,a C-V physical model of Schottky contact is established.The fitting coefficients of ? and ? are introduced to illustrate the influence of interfacial state and series resistance on C-V characteristics.Through quantitative calculation,the various components of capacitance are analyzed by combining the relevant physical mechanisms.The calculated value is fitted with the experimental data,and the fitting result is satisfactory.The C-V curves at different frequencies are fitted and analyzed.It is found that the value of ? decreases with the increased of frequency,and the value of ? increases with the increased of frequency.The decreasing trend of capacitance value after peak is slower.The influence of defects on capacitance is also considered.Combined with the fitting results,it is found that the experimental value is larger than the calculated value at the lower voltage.This phenomenon is caused by the effect of defects.Then,the electrical characteristics of the infrared detector with In Ga As/In P PIN structure are studied.Through I-V curves,the mechanism of dark current and the influence factors under different bias voltage are analyzed.From the C-V curve,the capacitance increases slowly at smaller bias voltage.With the increased of voltage,the amplitude of capacitance increases greatly.When the voltage increases a certain value,the capacitance will appear a peak value,and then the capacitance value will decrease with the increased of applied bias voltage.The phenomenon of negative differential capacitance is also found from the C-V curve,which is caused by the existence of defects,because under a certain voltage and frequency,the effect of defect on carrier transport process is more important than that of interface state.A C-V physical model is built for the peak phenomenon.In this model,the components of the capacitance are analyzed by combining the physical mechanism.Through the quantitative calculation,the component of capacitance and fitting value with experimental data are obtained.By fitting the C-V curves at different frequencies,it is found that the fitting results are not very good at a certain voltage.Because of the defects,the experimental data is larger than the calculated value.After that,a C-f model is established to study the relationship between capacitance and frequency.By the C-f model,the capacitance decreases qualitatively with the increased of frequency.This is consistent with the experimental phenomenon.