Study On Antimony-based Compound Semiconductor Superlattice Infrared Photodetectors

Antimony-based compound semiconductor superlattice(SL)infrared photodetector,as a new type infrared technology,is a research hotspot in the field of infrared detection.These photodetectors are based on the III-V compound semiconductor,using accurately controlled material epitaxy technology to make specific structure to detect the infrared radiation.The detective range of the antimony-based superlattice can cover 1?m to 30?m by changing the thickness of each layer of material in the structure.Owing to the advantages in the superlattice detector,such as the mature material growth and device fabrication processes,high uniformity,anti-radiation performance and so on,the detectors have attracted extensive research.This dissertation focuses on the InGaAs/GaAsSb and InAs/GaSb type-II SL infrared photodiodes.The main contents are listed as follows:1.The growth process of GaAsSb material on InP substrate was studied.And the growth process was simulated with the non-equilibrium thermodynamic model.On this bias,the high quality of InGaAs/GaAsSb type II SL material were obtained,and then the optical properties were characterized by photoluminescence(PL).Due to the bending effect of the energy band,a bule-shift of the energy peak with the increase of excitation power was observed.The dependence of the peak energy on temperature was analyzed.The effect of Be doping temperature on the properties of superlattice was studied.P-type InGaAs / GaAsSb type II superlattices were obtained by the compensation of Be.Detectors with different absorption layer thickness and compensation doping was prepared and characterized.Results show that the increase of the absorption layer thickness to the quantum efficiency of the device is limited,and the quantum efficiency can be improved significantly using compensating doping technique.Finally,320×256 focal plane array(FPA)devices were successfully fabricated.The mean peak detectivity is 4.3×1011 cm?Hz1/2?W-1 and uniformity is about 12% at temperature 200 K.2.The material of InAs/Ga Sb type II SL with pB?Bn structure was grown.The lattice mismatch between the GaSb and the absorption layer ?a/a is as small as 2.1×10-5,the full width of the half maximum of the-1 order satellite peak is 21.6 arc seconds.The mechanism of the below bandgap optical absorption in GaSb was studied,and the optical phonon and ionization impurity scattering is the dominated in the GaSb substrate.As the enhancement of GaSb transmittance by substrate thinning is limited,the substrate was totally removed by selective etching in the further fabrication process.The design of package scheme and experimental verification of the encapsulation of the FPA were proposed and optimized to solve the thermal mismatch.Finally,the 12 ?m 320×256 FPA devices were successfully fabricated.3.The prepared FPA device has a 50% cutoff wavelength of 12 ?m at 80 K.By fitting the curves of dark current densities and voltage,it is found that the dark currents in the temperature above 70 K were dominated by the diffusion currents,while dominated by generation-recombination currents when temperature was below 70 K.The performance of the devices were measured and analyzed.The inject efficiency of the read out circuit is the main factor that affect the response of the FPA.The emergence of most bad-pixels is due to the poor performance of the detectors,the rest is due to the poor connection.Through the feedback optimization of the device preparation process,320×256 integrated detector cooler assembly(IDCA)was obtained.At the temperature of 60 K,the mean peak detectivity is 7.2×1011 cm?Hz1/2?W-1,the noise equivalent differential temperature is 29.2 mK,the non-uniformity is 7.8% and the percentage of the bad-pixels was 2.7%.4.The ? radiation effect on InAs/GaSb type II SL detector was studied.The current-voltage characteristics of the devices did not change significantly with increase of the irradiation dose.By combining the real-time I-V curves at different irradiation doses and the evolution of the current with time after the irradiation,the damage and the corresponding mechanism of the ?-irradiation were analyzed.Under zero bias and small reverse bias,the radiation damage is dominated by the transient ionization effect.While under large reverse bias,the radiation damage is dominated by the displacement effect.The performances of the device before and after irradiation were compared and analyzed,it is found that irradiation did not affect the basic performance of the detector,but would affect the readout circuit,leading to its working state changes or even failure.