Ga<inf>1-x</inf>Al<inf>x</inf>Sb avalanche photodiodes: Resonant impact ionization with very high ratio of ionization coefficients

1981 ◽  
Vol 17 (2) ◽  
pp. 284-288 ◽  
Author(s):  
O. Hildebrand ◽  
W. Kuebart ◽  
K. Benz ◽  
M. Pilkuhn
Keyword(s):  
Impact Ionization ◽  
Avalanche Photodiodes ◽  
High Ratio ◽  
Ionization Coefficients ◽  
Very High

Determination of Impact Ionization Coefficients Measured from 4H Silicon Carbide Avalanche Photodiodes

2007 ◽  
Vol 556-557 ◽  
pp. 339-342 ◽  
Author(s):  
W.S. Loh ◽  
C. Mark Johnson ◽  
J.S. Ng ◽  
Peter M. Sandvik ◽  
Steve Arthur ◽  
...  
Keyword(s):  
Impact Ionization ◽  
Avalanche Photodiodes ◽  
Submicron Devices ◽  
Illuminating Light ◽  
Factor Data ◽  
Ionization Coefficients ◽  
P Type ◽  
Dark Currents ◽  
The Impact

Hole initiated avalanche multiplication characteristics of 4H-SiC avalanche photodiodes have been studied. The diodes had n+-n-p SiC epitaxial layers grown on a p-type substrate. These 1 mm2 devices had very low dark currents and exhibited sharp breakdown at voltages of approximately 500V. The diodes multiplication characteristics appeared to be identical when the wavelength of the illuminating light from the top varied from 288 to 325nm, implying that almost pure hole initiated multiplication was occurring. The multiplication factor data were modelled using a local multiplication model with impact ionization coefficients of 4H-SiC reported by various authors. The impact ionization coefficients extracted from submicron devices by Ng et al. were found to give accurate predictions for multiplication factors within the uncertainties of the doping levels. This result suggests that their ionization coefficients can be applied to thicker bulk 4H-SiC structures.

scholarly journals Estimates of Impact Ionization Coefficients in Superlattice-Based Mid-Wavelength Infrared Avalanche Photodiodes

2003 ◽  
Vol 799 ◽  
Author(s):  
C. H. Grein ◽  
K. Abu El-Rub ◽  
M. E. Flatté ◽  
H. Ehrenreich
Keyword(s):  
Valence Band ◽  
Impact Ionization ◽  
Energy Gap ◽  
Avalanche Photodiodes ◽  
Threshold Energy ◽  
Type Ii ◽  
Band Engineering ◽  
Type Ii Superlattice ◽  
Low Threshold ◽  
Ionization Coefficients

ABSTRACTWe describe band engineering strategies to either enhance or suppress electron-initiated impact ionization relative to hole-initiated impact ionization in type II superlattice mid-wavelength infrared avalanche photodiodes. The strategy to enhance electron-initiated impact ionization involves placing a high density of states at approximately one energy gap above the bottom of the conduction band and simultaneously removing valence band states from the vicinity of one energy gap below the top of the valence band. This gives the electrons a low threshold energy and the holes a high one. The opposite strategy enhances hole-initiated impact ionization. Estimates of the electron (α) and hole (β) impact ionization coefficients predict that α/β>>1 in the first type of superlattice and α/β<<1 in the second type.

Mean multiplication gain and excess noise factor of GaN and Al0.45Ga0.55N avalanche photodiodes

2020 ◽  
Vol 92 (1) ◽  
pp. 10301
Author(s):  
Tat Lung Wesley Ooi ◽  
Pei Ling Cheang ◽  
Ah Heng You ◽  
Yee Kit Chan
Keyword(s):  
Electric Field ◽  
Impact Ionization ◽  
Avalanche Photodiodes ◽  
Monte Carlo Model ◽  
Noise Factor ◽  
Excess Noise ◽  
Excess Noise Factor ◽  
Multiplication Gain ◽  
Ionization Coefficients ◽  
The Impact

In this work, Monte Carlo model is developed to investigate the avalanche characteristics of GaN and Al0.45Ga0.55N avalanche photodiodes (APDs) using random ionization path lengths incorporating dead space effect. The simulation includes the impact ionization coefficients, multiplication gain and excess noise factor for electron- and hole-initiated multiplication with a range of thin multiplication widths. The impact ionization coefficient for GaN is higher than that of Al0.45Ga0.55N. For GaN, electron dominates the impact ionization at high electric field while hole dominate at low electric field whereas Al0.45Ga0.55N has hole dominate the impact ionization at higher field while electron dominate the lower field. In GaN APDs, electron-initiated multiplication is leading the multiplication gain at thinner multiplication widths while hole-initiated multiplication leads for longer widths. However for Al0.45Ga0.55N APDs, hole-initiated multiplication leads the multiplication gain for all multiplication widths simulated. The excess noise of electron-initiated multiplication in GaN APDs increases as multiplication widths increases while the excess noise decreases as the multiplication widths increases for hole-initiated multiplication. As for Al0.45Ga0.55N APDs, the excess noise for hole-initiated multiplication increases when multiplication width increases while the electron-initiated multiplication increases with the same gradient at all multiplication widths.

scholarly journals Experimental evaluation of impact ionization coefficients in AlxGa1−xN based avalanche photodiodes

2006 ◽  
Vol 89 (18) ◽  
pp. 183524 ◽  
Author(s):  
Turgut Tut ◽  
Mutlu Gokkavas ◽  
Bayram Butun ◽  
Serkan Butun ◽  
Erkin Ulker ◽  
...  
Keyword(s):  
Experimental Evaluation ◽  
Impact Ionization ◽  
Avalanche Photodiodes ◽  
Ionization Coefficients

Avalanche Multiplication and Impact Ionisation in Separate Absorption and Multiplication 4H-SiC Avalanche Photodiodes

2008 ◽  
Vol 600-603 ◽  
pp. 1207-1210
Author(s):  
W.S. Loh ◽  
J.P.R. David ◽  
Stanislav I. Soloviev ◽  
H.Y. Cha ◽  
Peter M. Sandvik ◽  
...  
Keyword(s):  
Electric Fields ◽  
Room Temperature ◽  
Impact Ionization ◽  
Avalanche Photodiodes ◽  
Extreme Environment ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Avalanche Multiplication ◽  
Impact Ionisation ◽  
Ionization Coefficients

The hole dominated avalanche multiplication characteristics of 4H-SiC Separate Absorption and Multiplication avalanche photodiodes (SAM-APDs) were determined experimentally and modeled using a local multiplication model. The 0.5x 0.5mm2 diodes had very low dark current and exhibited sharp, uniform breakdown at about 580V. The data agree with modeling result using extrapolated impact ionization coefficients reported by Ng et al. and is probably valid for electric fields as low as ~0.9MV/cm at room temperature provided that both the C-V measurements and electric field determination in this work are correct. The packaged devices demonstrate a positive temperature coefficient of breakdown voltage for temperatures ranging from 100K to 300K which is a desired feature for extreme environment applications.

Controlled Release of Metformin Hydrochloride I. In vitro Release from Physical Mixture Containing Xanthan Gum as Hydrophilic Rate Retarding Polymer

1970 ◽  
Vol 4 (1) ◽  
Author(s):  
Mashkura Ashrafi ◽  
Jakir Ahmed Chowdhury ◽  
Md Selim Reza
Keyword(s):  
Controlled Release ◽  
Xanthan Gum ◽  
In Vitro Release ◽  
Correlation Coefficients ◽  
High Ratio ◽  
Water Soluble ◽  
Metformin Hydrochloride ◽  
Model Drug ◽  
Very High

Capsules of different formulations were prepared by using a hydrophilic polymer, xanthan gum and a filler Ludipress. Metformin hydrochloride, which is an anti-diabetic agent, was used as a model drug here with the aim to formulate sustained release capsules. In the first 6 formulations, metformin hydrochloride and xanthan gum were used in different ratio. Later, Ludipress was added to the formulations in a percentage of 8% to 41%. The total procedure was carried out by physical mixing of the ingredients and filling in capsule shells of size ‘1’. As metformin hydrochloride is a highly water soluble drug, the dissolution test was done in 250 ml distilled water in a thermal shaker (Memmert) with a shaking speed of 50 rpm at 370C &plusmn 0.50C for 6 hours. After the dissolution, the data were treated with different kinetic models. The results found from the graphs and data show that the formulations follow the Higuchian release pattern as they showed correlation coefficients greater than 0.99 and the sustaining effect of the formulations was very high when the xanthan gum was used in a very high ratio with the drug. It was also investigated that the Ludipress extended the sustaining effect of the formulation to some extent. But after a certain period, Ludipress did not show any significant effect as the pores made by the xanthan gum network were already blocked. It is found here that when the metformin hydrochloride and the xanthan gum ratio was 1:1, showed a high percentage of drug release, i.e. 91.80% of drug was released after 6 hours. But With a xanthan gum and metformin hydrochloride ratio of 6:1, a very slow release of the drug was obtained. Only 66.68% of the drug was released after 6 hours. The percent loading in this case was 14%. Again, when Ludipress was used in high ratio, it was found to retard the release rate more prominently. Key words: Metformin Hydrochloride, Xanthan Gum, Controlled release capsule Dhaka Univ. J. Pharm. Sci. Vol.4(1) 2005 The full text is of this article is available at the Dhaka Univ. J. Pharm. Sci. website

scholarly journals Impact Ionization Coefficients in (AlₓGa₁₋ₓ)0.52In0.48P and AlₓGa₁₋ₓAs Lattice-Matched to GaAs

2021 ◽  
pp. 1-6
Author(s):  
Harry I. J. Lewis ◽  
Liang Qiao ◽  
Jeng Shiuh Cheong ◽  
Aina N. A. P. Baharuddin ◽  
Andrey B. Krysa ◽  
...  
Keyword(s):  
Impact Ionization ◽  
Ionization Coefficients ◽  
Lattice Matched

Temperature Dependence of Hole Impact Ionization Coefficient in 4H-SiC Photodiodes

2009 ◽  
Vol 615-617 ◽  
pp. 311-314 ◽  
Author(s):  
W.S. Loh ◽  
J.P.R. David ◽  
B.K. Ng ◽  
Stanislav I. Soloviev ◽  
Peter M. Sandvik ◽  
...  
Keyword(s):  
Phonon Scattering ◽  
Impact Ionization ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Different Temperatures ◽  
Ionization Coefficients ◽  
Increasing Temperature ◽  
The Impact ◽  
Good Agreement ◽  
Ionization Rates

Hole initiated multiplication characteristics of 4H-SiC Separate Absorption and Multiplication Avalanche Photodiodes (SAM-APDs) with a n- multiplication layer of 2.7 µm were obtained using 325nm excitation at temperatures ranging from 300 to 450K. The breakdown voltages increased by 200mV/K over the investigated temperature range, which indicates a positive temperature coefficient. Local ionization coefficients, including the extracted temperature dependencies, were derived in the form of the Chynoweth expression and were used to predict the hole multiplication characteristics at different temperatures. Good agreement was obtained between the measured and the modeled multiplication using these ionization coefficients. The impact ionization coefficients decreased with increasing temperature, corresponding to an increase in breakdown voltage. This result agrees well with the multiplication characteristics and can be attributed to phonon scattering enhanced carrier cooling which has suppressed the ionization process at high temperatures. Hence, a much higher electric field is required to achieve the same ionization rates.

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