# Possible realization of near optimum efficiency from n-Si-Ge/p-Ge-Si DDR Hetero Structure IMPATT Diode

17 Mar 2011-pp 1-5

TL;DR: In this article, a p-n junction under reverse bias avalanche breakdown condition is capable of producing high frequency rf power in Impatt mode for operation at 15 and 96 GHz.

Abstract: A p-n junction under reverse bias avalanche breakdown condition is capable of producing high frequency rf power in Impatt mode With the advancement of Device Technology, the present state of art reports realization of alloy Si-Ge junction, Si-Ge hetero junction Introduction of a n-Ge and p-Ge impurity bumps near the junction face on respective side of Si p-n junction leaves an asymmetrical hetero structure junction which has become the scope of study of this paper for operation at 15 and 96 GHz Three tier sophisticated computer algorithm has been framed and used for Impatt analysis of resulting n-Si-Ge/p-Ge-Si Hetero Structure reveals realization of device efficiency as high as 296% (Theoretical Optimum Efficiency of Impatt Diode=31%) and also high value of negative conductance Presence of Ge layer near junction and an order high carrier ionization rate in Ge compared to Si localizes the avalanche zone, which pushes the efficiency and RF power generation Similar results are also noticed for 96 GHz operations The performance from this structure is observed to be superior by considerable extent as compared to Si and Ge homo structure However the complementary hetero structure having the form n-Ge-Si/p-Si-Ge is observed to exhibit performance almost on par to Si and Ge homo structures The results are highly encouraging which may make Si-Ge Hetero Structure Diode as a microwave generator

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14 Nov 2014

TL;DR: Results suggest that Si0.9Ge0.1 shows more negative resistance than the conventional one, and thus it may be considered as the suitable alternative choice for microwave source.

Abstract: Negative resistivity of Si and Si0.9Ge0.1 DDR IMPATT diode are numerically computed using double iterative method and modified Runge-Kutta method and results are compared for identical input parameters. Simulation is based on simultaneous solution of Poisson's equation, continuity equation and carrier diffusion equation in addition with the effect of mobile space charge subject to the appropriate boundary conditions at the edges of depletion layer. Effect of junction temperature and current density on resistance is evaluated for optimum performance in CE mode. Peaks of the resistivity profile depend on temperature, bias current and frequency of operation. Results suggest that Si0.9Ge0.1 shows more negative resistance than the conventional one, and thus it may be considered as the suitable alternative choice for microwave source.

5 citations

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TL;DR: In this article, the performance of wide-bandgap p-SiC/n-GaN heterojunction double-drift region (DDR) IMPATT diode is investigated for the first time.

Abstract: Nowadays, the immature p-GaN processes cannot meet the manufacturing requirements of GaN impact ionization avalanche transit time (IMPATT) diodes. Against this backdrop, the performance of wide-bandgap p-SiC/n-GaN heterojunction double-drift region (DDR) IMPATT diode is investigated in this paper for the first time. The direct-current (DC) steady-state, small-signal and large-signal characteristics are numerically simulated. The results show that compared with the conventional GaN single-drift region (SDR) IMPATT diode, the performance of the p-SiC/n-GaN DDR IMPATT proposed in this design, such as breakdown voltage, negative conductance, voltage modulation factor, radio frequency (RF) power and DC-RF conversion efficiency have been significantly improved. At the same time, the structure proposed in this design has a larger frequency bandwidth. Due to its greater potential in the RF power density, which is 1.97 MW/cm2 in this study, indicates that the p-SiC/n-GaN heterojunction provides new possibilities for the design and manufacture of IMPATT diode.

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TL;DR: In this article, a novel n-In x Ga1-x N/N-gallium nitride (GaN) homotype heterostructure is proposed instead of P-GaN/N -GaN homostructure to produce impactionization-avalanche-transit-time (IMPATT) diode.

Abstract: In this work, a novel n-In x Ga1- x N/N-gallium nitride (GaN) homotype heterostructure is proposed instead of P-GaN/N-GaN homostructure to produce impact-ionization-avalanche-transit-time (IMPATT) diode. Conventional GaN IMPATT device will lose its working ability due to the immature p-type GaN, so this work predicts that the n-In x Ga1- x N/N-GaN IMPATT diode can be an alternative to the GaN p-n IMPATT diode; thus, the difficulty of the p-type doping process is avoided. The dc and RF large-signal output characteristics with different compositions are investigated in detail. The simulation results show that the power and efficiency of the novel structure device increase when the In composition increases. When the In composition is greater than 0.4, the performance of the homotype heterojunction IMPATT is better than that of p-n IMPATT. Moreover, homotype heterojunction IMPATT is better in frequency bandwidth, and it can hold greater bias current density than p-n IMPATT. Meanwhile, the performance of homotype heterojunction IMPATT does not depend on the thickness of the InGaN layer, but it decreases as the thickness of the p-type region in p-n IMPATT increases. As it has greater potential in the application, this work brings a reference for the design and manufacture of IMPATT devices based on wide bandgap semiconductor materials, especially GaN materials.

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TL;DR: In this article, electric field profile, normalized current density, breakdown voltage and conversion efficiency of Si/Si 0.9Ge 0.1 DDR IMPATT are numerically computed and results are compared with Si DDR diode for optimized input bias current.

Abstract: In this paper, electric field profile, normalized current density, breakdown voltage and conversion efficiency of Si/Si0.9Ge0.1 DDR IMPATT are numerically computed and results are compared with Si DDR diode for optimized input bias current. Double iterative technique is used for computational purpose which is based on simultaneous numerical solution of Poisson's equation, carrier diffusion equation and continuity equation in addition with the effect of mobile space charge. Electric field and normalized current profiles are obtained subject to the appropriate boundary conditions. Breakdown voltage and conversion efficiency are calculated for optimized input bias current density. Doping concentration is so chosen to obtain punch-through effect. Results are useful for small-signal analysis at microwave and millimeterwave frequency range.

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01 Nov 2015

TL;DR: In this paper, the conductance, susceptance, reactance, quality factor and noise factor of the Si09Ge01IMPATT diode were numerically computed using double iterative method and modified Runge-Kutta method when device is operated at millimeterwave frequency region.

Abstract: Conductance, susceptance, reactance, quality factor and noise factor of Si09Ge01IMPATT diode are numerically computed using double iterative method and modified Runge-Kutta method when device is operated at millimeterwave frequency region. Poisson's equation, carrier diffusion equation and continuity equation are simultaneously solved are in presence of mobile space charge subject to the appropriate boundary conditions at the edges of depletion layer. Input current density is varied to compute the small-signal parameters within practical limit, and stability of the device is studied in terms of quality factor from the G-B plot. Simulation suggests that the heterostructure diode is more stable than homostructure IMPATT, similar like the noise factor. Result is significant for operating the diode as alternative but more efficient microwave source than conventional one.

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##### References

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Bell Labs

^{1}TL;DR: In this paper, a general small-signal theory of the avalanche noise in IMPATT diodes is presented, which is applicable to structures of arbitrary doping profile and uses realistic (α
eq \beta in Si) ionization coefficients.

Abstract: A general small-signal theory of the avalanche noise in IMPATT diodes is presented. The theory is applicable to structures of arbitrary doping profile and uses realistic ( \alpha
eq \beta in Si) ionization coefficients. The theory accounts in a self-consistent manner for space-charge feedback effects in the avalanche and drift regions. Two single-diffused n-p diodes of identical doping profile, one of germanium and the other of silicon, are analyzed in detail. For description of the noise of the diodes as small-signal amplifiers the noise measure M is used. Values for M of 20 dB are obtained in germanium from effects in the depletion region only, i.e., when parasitic end region resistance is neglected. Inclusion of an assumed parasitic end resistance of one ohm for a diode of area 10-4cm2produces the following noise measure at an input power of 5×104W/cm2, and at optimum frequency: germanium 25 dB, silicon 31 dB. For comparison, a noise figure of 30 dB has been reported [1] for a germanium structure of the same doping profile as used in the calculations. Measurements of silicon diodes of the same doping profile are not available, but typically silicon diodes give 6-8 dB higher noise figures than germanium diodes of comparable doping profile.

229 citations

### "Possible realization of near optimu..." refers methods in this paper

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TL;DR: The development, operating principles, and state-of-the-art of various diode and transistor structures are reviewed.

Abstract: Starting with exploratory work in the 1930s and development work in the 1940s a variety of two-terminal and three-terminal solid-state device structures have been proposed, fabricated, and developed. This work parallels the development effort on vacuum electronic devices, and the two technologies share many applications. The solid-state and vacuum electronic devices work in tandem to enable numerous commercial and military systems. Solid-state device development is closely linked to semiconductor materials growth and processing technology, and advances such as the introduction of heterojunction growth technology, permit complex multiple layer device structures to be fabricated and optimized for maximized device performance. This work has been very successful and a variety of high-performance diodes and transistors are now available for use from UHF into the millimeter-wave spectrum, approaching terahertz frequencies. The development, operating principles, and state-of-the-art of various diode and transistor structures are reviewed.

89 citations

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TL;DR: Ionization rates in 〈100〉 germanium are determined experimentally in this paper, where α and β are ionization rates for electrons and holes, respectively, and E is the electric field.

Abstract: Ionization rates in 〈111〉 and 〈100〉 germanium are determined experimentally. The ionization rates obtained are expressed as α=2.72×106 exp(−1.1×106/E), β=1.72×106 exp(−9.37×105/E) for 〈111〉 and α=8.04×106 exp(−1.4×106/E), β=6.39×106 exp(−1.27×106 /E) cm−1 for 〈100〉 where α and β are ionization rates for electrons and holes, respectively, and E is the electric field. Hole‐ to electron‐ionization‐rate ratios of 〈100〉 Ge are found to be greater than those of 〈111〉 Ge. The multiplication noise power of Ge avalanche photodiodes calculated by using the ionization rates obtained shows good agreement with experimental results.

40 citations

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TL;DR: In this paper, a p-Ge thin film was applied to n-Si substrates using molecular beam epitaxy and electron-beam evaporation, with processing temperatures less than 450 ◦ C, to be compatible with back-end silicon processing.

Abstract: P–n hetero-junctions were fabricated by depositing p-Ge thin films on n-Si substrates using molecular beam epitaxy and electron-beam evaporation, with processing temperatures less than 450 ◦ C, to be compatible with back-end silicon processing. The surface preparation of the Si substrate prior to Ge deposition was found to significantly affect the crystallinity of the deposited Ge layers and, hence, the p–n photodetector diode characteristics. The quality of the deposited Ge layers was inferred both through electrical and optical measurements as well as through structural characterization, i.e. X-ray diffraction (XRD). Surface desorption treatments to remove adsorbed hydrogen, oxygen and hydrocarbons were attempted to improve the Si surface quality to increase the minority carrier diffusion lengths and minimize dark current densities. Hydrogen desorption treatment at 450 ◦ C prior to Ge deposition gave the best performance with diffusion lengths greater than 25 nm and dark currents of 0.3 mA/cm 2 . The observed performance from the p–n diodes is expected to be sufficient for fabricating

35 citations

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TL;DR: In this article, electron transport in unstrained Si1-x Gex (0≤x ≤ 0.4) alloy is studied using the Monte Carlo (MC) simulation technique.

Abstract: Electron transport in unstrained Si1-x Gex (0≤x ≤0.4) alloy is studied in the present work using the Monte Carlo (MC) simulation technique. Electron transport characteristics (drift velocity, impact ionization (II) coefficient, etc.) are evaluated over a wide range of electric fields. It is found that not only low-field mobility but also saturation velocity and impact ionization coefficients are reduced with increasing Ge fraction due to alloy scattering. More importantly, the high-energy ( e>2 eV) electron population is reduced to a much greater extent than the ionization coefficient. Simple analytical expressions for electron low-field mobility, saturation velocity and II coefficient which can be easily implemented in device simulation programs are proposed.

28 citations

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