Precision Etching of Thin Doped Silicon Layers Borovkova, A. Yu; Grischina, T. N.; Matyuhina, E. S.
Journal of communications technology & electronics,
03/2018, Letnik:
63, Številka:
3
Journal Article
Recenzirano
The optimum etchant composition for precise removal of a thin high-doped silicon gettering layer is determined. It is found that the best-controlled etching is provided by the following composition: ...HNO
3
: HF: CH
3
COOH = 40: 1: 1. This composition etches the entire gettering layer away while preserving the required thickness of the contact layer, which prevents the space-charge region of the
p–n
junction from emerging at the back surface of the base of a photosensitive element. Thus, this etchant provides an opportunity to reduce the magnitude of dark currents and raise the percentage yield.
A topical problem of photoelectronics is the development of array photodetector devices of the near infrared spectral range based on the In
x
Ga
1–
x
As/InP epitaxial layers of the megapixel format. ...In this paper, we present the results of studies of current–voltage characteristics of photosensitive elements in arrays of the 320 × 256 format with a step of 30 μm based on heteroepitaxial structures with an InGaAs absorbing layer on InP short-wave infrared substrates. Arrays of photosensitive elements (PSEs) are fabricated using planar, mesa, and mesa planar technologies based on
nB
(Al
0.48
In
0.52
As)
p
-structures. In arrays produced using the mesa planar technology based on
nB
(Al
0.48
In
0.52
As)
p
-structures, small dark current and ampere–watt sensitivity to IR radiation of the 1–1.7 μm range are shown to combine successfully at low bias voltages. Electrophysical parameters of functional layers of initial heteroepitaxial
n-B-p
structures affect efficiently the dark currents and ampere–watt sensitivity of the array elements. Based on these studies, parameters of the
n-B
(Al
0.48
In
0.52
As) functional layers of
p
-structures were optimized and high-efficiency photodiode arrays of the 320 × 256 format with a step of 30 μm and structures of the 640 × 512 format with a step of 15 μm were fabricated with a defectiveness not exceeding 0.5%.
Photoresistors with thermoelectric cooling of photosensitive elements are developed in the topology of the five-digit Gray code using the Cd
x
Hg
1–
x
Te heteroepitaxial structures produced with the ...aid of molecular-beam epitaxy. The photoresistors can be used to detect pulsed laser radiation with a wavelength of 10.6 μm. The dependence of the signal-to-noise ratio on the composition of the narrow-band-gap working layer of the epitaxial structure and the structure of the photoresistor is studied.
Parameters of multi-row photodetectors (PDs) based on HgCdTe heteroepitaxial structures of different formats, including 288 × 4, 480 × 6, 576 × 4, and 576 × 6, with a step of 28 to 14 microns are ...studied. Owing to the choice of a
N
+
/
P
-/
р
-architecture, PDs operate at elevated temperatures in the time delay and integration (TDI) mode with the implementation of the analog mode of TDI and the replacement of defective elements directly in the readout LSI. The PDs are capable of forming high-definition images of the 768 × 576 format at a frame rate of 50 Hz in real time. For the multi-row PDs, high photoelectric parameters were obtained: the detection capacity at the maximum of the spectral sensitivity
D
* ≥ 5 × 10
12
cm W
–1
Hz
1/2
at temperatures
Т
~ 170–200 K and the number of working channels is not less than 99.0%.
Characteristics of external conditions are studied in spectral intervals of 0.4–0.9 and 1.4–1.7 μm. The advantages of photodetector arrays that are sensitive in a spectral interval of 1.4–1.7 μm are ...demonstrated for applications in night-vision devices.
The time of independent operation
t
ind
of indium antimonide photoresistors and photodiodes and photoresistors based on Cd
х
Hg
1–
х
Te (
х
~ 0.3) heterostructures deeply cooled with a Joule–Thomson ...throttling system is investigated. The largest independent operation time (taut ≥ 28 s) was obtained for Cd
х
Hg
1–
х
Te (
х
~ 0.3) photoresistors. Time
t
ind
of the photoresistors and photodiodes is found to be related to the temperature of transition of the semiconductor materials from the impurity region to the intrinsic region. The possibility of increasing time
t
ind
of the photodetectors by optimizing the requirements for the characteristics of InSb and Cd
х
Hg
1–
х
Te is discussed.
A model for calculation of the angle of misorientation between the reflecting crystallographic planes and the plane of the semiconductor surface of a sample by means of high-resolution X-ray ...diffractometry has been developed. The model can minimize mechanical instrument errors, including the positioning and moving inaccuracies, and determine the optimum parameters of sample position with respect to the incident radiation for correct investigations of the perfection of the crystal structure. The principle of conduction of the experiment and the mathematical model used for processing of the obtained data are described. To find macrodefects of the crystal structure, in particular, blocks, the map of the distribution of parameters of the the rocking curve of the entire sample was obtained using the developed model. This allowed determination of the blocks boundaries and their mutual orientation in the directions longitudinal relative to the wafer. The model was tested on a wafer cut from a bulk indium antimonide single crystal grown by the Czochralski method and subjected to chemical-dynamic and chemical-mechanical polishing.
The results of the development of a thermal imaging device based on the FEM10M photodetector produced by the Orion Research and Production Association are presented. As a result of the implementation ...of measures for improvement of the TPK-Z thermal imaging camera so as to comply with a domestic photodetector, the TPK-ZR thermal imaging device based on a domestic multirow array was developed, tuned, and tested. The minimum allowed temperature difference (MATD) and noise equivalent temperature difference (NETD) characteristics of the device are at least as good as the corresponding characteristics of a thermal imager using a foreign photodetector. The complex of image processing algorithms used in the TPK-ZR device makes it possible to obtain thermal images whose quality is not worse then the quality of the images obtained with the TPK-Z device. Further development of the obtained result can be implementation of a series of measures aimed at achieving full automation of calibration processes in the thermal imager.
Values of the absorption coefficient of InGaAs structures grown by means of gaseous-phase epitaxy from metaloranic compounds have been studied and calculated. Experimental data have been compared to ...the theoretical model of the absorption spectrum based on the phenomenon of fundamental absorption and the general theory of direct interband optical transitions. The energy gap width has been graphically calculated from the slope of the experimental absorption characteristic.
320 × 256 avalanche array photodetector on the basis ternary alloys of the A
3
B
5
group with an InGaAs absorbing (in the band of 0.9–1.7 μm) layer and InAlAs barrier layer is studied. The array of ...320 × 256 elements was fabricated in a nBp nanoheterostructure by the mesa technology. The number of imperfect elements, the dependence of the dark current on the bias voltage, and the avalanche gain factor are measured.
