The annealing effects of rapid thermal processing in N2 from 350 °C to 500 °C for 60 s on Ni/Pt/Au contacts to p-InAlAs have been investigated. The result indicated that the contacts were all Schottky contacts and lowest barrier height(0.67eV) was achieved at about 450 °C. Then we used evacuated sealed-ampoule Zn diffusion method to form a heavily doped layer on p-InAlAs layer of the same sample. The diffusion conditions were 530 °C &4 min and 530 °C
&8 min, respectively. Also Ni/Pt/Au contacts were deposited on the two samples and annealed at 450 °C &60 s. Although I-V characteristics which were measured indicated that a heavily doped layer is beneficial for the cantacts properties, the contacts were still Schottky contacts and the barrier heights were reduced to 0.54 eV and 0.57 eV for the two samples. Finally, we investigated contacts property of Ti/Pt/Au on p-In0.52Al0.48As of the sample which is Zn-diffused at 530 °C for 4 min. The sample was annealed at 450 °C for 60 s and the contact resistivity of the contacts was determined using the transfer line model measurements. Low resistance ohmic contacts (ρc=8.88×10-4 Ωcm2) were achieved. The results indicated that the contacts property is controlled by chemical and metallurgical reaction between the contact metal and the InAlAs layer, and a heavily doped layer is beneficial to contact properties.
A chemistry of halogen mixed with neural or inert gas is mostly used for ICP etching of III-V compound semiconductor.
The neural or inert gas has an effect of desorption and dilution, on the other hand, damages in the lattice due to ion
bombardment are induced, which result in difficulties in improving the performances of detectors. Good desorption and
passivation was obtained by using a new etching technology with the mixed gas of methane and hydrogen instead of
neural or inert gas, and the damages caused by physical bombardment were much less because of the small quality of
radical. The sample etched by using this technology was compared with the ones by using etching of neural or inert gas.
The influences of ICP etching process parameters on etch rate, surface roughness and surface damage were investigated
by using orthogonal experimental design. The methods of scanning electron microscopy (SEM) and X-ray Diffraction
(XRD) were used to investigate the surface profile and surface damage respectively. And according to the experimental
results, the process parameters are optimized. Finally, a feasible etching technology with low damage, good surface
profile and good controllability was achieved.
This article presents the fabrication of the front-illuminated planar type InGaAs sub-pixels infrared detector with the cutoff wavelength 1.68µm based on the lateral collection effect of photogenerated carriers. The detector with the dimension of 385µm×500µm consists of five sub-pixels and each of which has two sub-elements. The electrical properties and photo response characteristics were investigated after the detector mounted on Dewar. The photoresponse map from Laser beam induced current (LBIC) method shows that the detector has good photoresponse uniformity at 296K which indicates the electron/hole pairs generated in the lateral collection regions are all collected by the nearest sub-elements. The minority carrier diffusion length Lp is about 19.6µm at 296K. The density of dark current is 13.4nA/cm2 at 100mV reverse bias and the peak detectivity is 3.4×1012cmHz1/2W-1 at room temperature. By reducing the diffusion region, the detector could effectively decrease the lattice damage and corrosion spots in the cap layer caused in the PN junction formation without sacrificing detector performance. Therefore, this structure could availably reduce the ratio of dead pixels, suppress the extension of photo-sensitive area and the optical cross-talk in photo detector arrays.
InxGa1-xAs ternary compound is suitable for detector applications in the shortwave infrared (1-3 μm) band. The alloy In0.53Ga0.47As is lattice-matched to InP substrate, which leads to high quality epitaxial layers. Consistently the In0.53Ga0.47As detector shows low dark current density and high detectivity at room temperature with wavelength response between 0.9 and 1.7 μm. In this paper, planar-type 24×1 linear InGaAs detector arrays with guard-ring structure were designed and fabricated based on n-i-n+ type InP/In0.53Ga0.47As/InP epitaxial structure by sealed-ampoule diffusion method. At first the dark current density is about 30~60 nA/cm2 at -0.1 V at room temperature. After modifications to the detector design and processing, the dark current density reduces to 2~9 nA/cm2 at -0.1 V at 293 K. The ideality factors simulated from I-V curves come close to 1 and less than the factors of previous detectors, which indicates that the dark current is dominated by diffusion current, while the generation-recombination current exhibits in the previous detectors. At the temperature of 293 K, the R0A of the detector reaches more than 1×107 Ω·cm2, the relative spectral response is in
the range of 0.9 μm to 1.68 μm, the mean peak responsivity is 1.2 A/W and the mean peak detectivity is more than 3.0×1012 cm·Hz1/2/W.
Scanning capacitance microscopy (SCM) and scanning spreading resistance microscopy (SSRM) both are capable of
mapping the 2-demensional carrier distribution in semiconductor device structures, which is essential in determining their electrical and optoelectronic performances. In this work, cross-sectional SCM1,2 is used to study the InGaAs/InP P-i-N junctions prepared by area-selective p-type diffusion. The diffusion lengths in the depth as well as the lateral
directions are obtained for junctions under different window sizes in mask, which imply that narrow windows may result in shallow p-n junctions. The analysis is beneficial to design and fabricate focal plane array of near infrared photodetectors with high duty-cycle and quantum efficiency. On the other hand, SSRM provides unparalleled spatial resolution (<10 nm) in electrical characterization3 that is demanded for studying low-dimensional structures. However, to derive the carrier density from the measured local conductance in individual quantum structures, reliable model for SSRM is necessary but still not well established. Based on the carrier concentration related transport mechanisms, i.e.
thermionic emission and thermionic field emission4,5, we developed a numerical model for the tip-sample Schottky
contact4. The calculation is confronted with SSRM study on the dose-calibrated quantum wells (QWs).
To improve the operability and rate of final products significantly, a novel process was proposed. Detectors with
cutoff wavelength at 1.7 μm and 2.4 μm were fabricated in different processes, and the electricity characteristics and
spectral response were measured. The novel process was analyzed by comparing the characteristics of the detectors. The
dark current and responsibility of the detectors with cutoff wavelength at 1.7 μm fabricated in the new process were
improved. However, the new process has negative effect on the detectors with cutoff wavelength at 2.4 μm. The pnjunction
degenerated and the leakage current increased sharply. In order to find the reasons of degeneration, the methods
of Auger electron spectroscopy (AES) and scanning capacitance microscope (SCM) were used. The results indicate that
the metal elements do not penetrate into the pn junction causing the sharp increase of leakage current, while the interface
states due to lattice mismatch are thermally activated causing the degeneration of pn- junction.