By adopting the vacuum sealed-ampoule technique, P-type doping of Zn elements in the lattice-mismatched NInAs0.6P0.4/i-In0.8Ga0.2As/N-InP heterostructure material was achieved to form PN junction. The diffusion mechanism of Zn in the material was studied using secondary ion mass spectrometry (SIMS) and scanning capacitance microscopy (SCM). Furthermore, the temperature-dependent photoelectric properties were investigated after the short-wave infrared (SWIR) detector was fabricated and packaged in a vacuum Dewar. The results indicate that the doped Zn elements in the material are not fully activated, leading to a PN junction depth smaller than the diffusion depth, and rapid thermal processing (RTP) does not affect the PN junction depth. The cutoff long-wavelength of the detector at 273K is 2.53 μm, and the peak detectivity reaches a peak value of 2.42×1011 cm•Hz1/2/W at 133K.
Based on collection effect of photogenerated carrier, the front-illuminated planar type InGaAs short-wave infrared (SWIR) detectors were fabricated by using N-InP/i-In0.53Ga0.47As/N-InP double-hetero structure materials. The series of detectors with the same dimension of 200μm×200μm contain several lateral collection regions and the width of each collection region is 15μm. The photoelectric characteristics of the photoresponse, I-V, spectral response and detectability of detectors with the lateral collection structure and normal structure were further analyzed. The build-in electrical field could effectively collect the electron/hole pairs generated in the lateral collection regions, so the photoresponse of lateral collection detector at 296 K is quite uniform by the laser beam induced current (LBIC) technology. Furthermore, the average peak detectivity and the density of dark current of the detectors with lateral collection structure reached 2.90× 1012 cm·Hz1/2/W and 3.94 nA/cm2 at -0.1 V respectively. It turns out that the lateral collection structure could effectively improve the dark current properties compared with the normal structure.
This article presents the fabrication of the front-illuminated planar type InGaAs infrared detector based on the lateral collection structure. The detector with the cutoff wavelength 1.7μm was fabricated on the NIN-type InP/InGaAs/InP hetero-structure materials with sealed-ampoule method using Zn3P4 as the diffusion source. And the detector with the dimension of 460μm×1000μm consists of four lateral collection regions and the width of each region is 15μm. Furthermore, the electrical properties and photo response characteristics were investigated between detectors with the lateral collection structure and normal structure. The Laser beam induced current (LBIC) map shows that the photoresponse of lateral collection InGaAs detector at 296 K is quite uniform and the photoresponse signals generated in the lateral collection regions are the same as them in PN junction regions. The lateral collection regions disappear from view since the electron/hole pairs generated in the regions are all collected by the electrical field of depletion region. It turns out that the average peak detectivity and the density of dark current of the detectors with lateral collection structure and normal structure is 3.22×1012 cm·Hz1/2/W and 3.00×1012 cm·Hz1/2/W, 4.85 nA/cm2 and 22 nA/cm2 at -100 mV respectively. Therefore, the lateral collection structure could substantially reduce the dark current by 70% compared with the normal structure.
In order to study the effect of different passivation films on the detector performance, the front-illuminated planar-type 256×1 element InGaAs/InP detectors were fabricated with SiNx film and SiO2 film. The SiNx film was deposited by plasma enhanced chemical vapor deposition (PECVD) and SiO2 film was deposited by magnetron sputtering technology. The electrical properties and photoresponse characteristics were investigated after the detector mounted on dewar. The photoresponse maps from laser beam induced current (LBIC) method show that the isolation of adjacent elements of the detector with SiNx film is better than the detector with SiO2 film. Furthermore, at room temperature the average density of dark current and the average peak detectivity of the two kinds of detector is 26.8 nA/cm2 and 41.2 nA/cm2 at 100 mV reverse bias, 1.21×1012 cm·Hz1/2/W and 1.08×1012 cm·Hz1/2/W respectively. Therefore, the detector with SiNx film deposited by PECVD could availably passivate the surface in comparison with the detector with SiO2 film by magnetron sputtering technology.
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