Multiplication Avalanche Photodiodes Research Articles

Al<inline-formula><tex-math>$_{\bf 0.52}$</tex-math></inline-formula>In<inline-formula><tex-math>$_{\bf 0.48}$</tex-math></inline-formula>P SAM-APD as a Blue-Green Detector

We demonstrate an ${\rm Al}_{0.52}{\rm In}_{0.48}{\rm P}$ homo-junction Separate Absorption Multiplication Avalanche Photodiode as a detector with narrow spectral response in the blue-green part of the optical spectrum. Due to its wide band-gap, this device has a dark current density of ${\rm cm}^{-2}$ at 99.9% of the breakdown voltage at room temperature. This device has a peak responsivity at 483 nm of 0.15 A/W when punched-through and is capable of an avalanche gain higher than 100.

A circuit modeling of SAGCM avalanche photodiode with additional layer and nonuniform electric field profile

This paper presents a new way to improve the speed of the separated absorption grading charge multiplication avalanche photodiode by adding a new thin charge layer between absorption and grading layers. In this method, we assume a nonuniform electric field in different regions of the structure. In addition, based on carrier rate equations, a circuit model of the proposed structure is extracted. Considering the trade-offs between thicknesses of layers, we try to acquire the optimum structure by setting the physical parameters. Finally, it is shown that, in comparison with the conventional structure, considerable improvements in the gain-bandwidth product and also breakdown voltage are achieved.

Comprehensive analysis of new near-infrared avalanche photodiode structure

The essential steps in simulations of modern separate absorption, grading, charge, and multiplication avalanche photodiode and their results are discussed. All simulations were performed using two commercial technology computer-aided design type software packages, namely Silvaco ATLAS and Crosslight APSYS. Comparison between those two frameworks was made and differences between them were pointed out. Several examples of the influence of changes made in individual layers on overall device characteristics have been shown. Proper selection of models and their parameters as well as its significance on results has been illustrated. Additionally, default values of material parameters were revised and adequate values from the literature were entered. Simulated characteristics of optimized structure were compared with ones obtained from measurements of real devices (e.g., current-voltage curves). Finally, properties of crucial layers in the structure were discussed.

Impact Ionization in Absorption, Grading, Charge, and Multiplication Layers of InP/InGaAs SAGCM APDs With a Thick Charge Layer

We present a general methodology for device-level simulation of multiplication, noise, and receiver sensitivity in separate absorption, grading, charge, and multiplication avalanche photodiodes (SAGCM APDs) with a thick charge layer. According to the best of our knowledge, it is the first time to report the experimental evidence for impact ionization in combination of absorption, grading, charge layer with multiplication layers for SAGCM APDs. A thick charge layer was adopted in our InP/InGaAs APDs, which provides us a chance to elucidate the contribution of the electric field in the charge layer to the overall performance for SAGCM APDs. In addition, thereby performance dependence of SAGCM APDs on the thickness of charge layer has also been discussed. An empirical formula is proposed to predict the thickness of the InP multiplication layer of APDs with different charge doping levels for optimization in noise performance. The technological significance of the device-level simulation on the design and development of SAGCM APDs has also been addressed.

An InGaAs/AlAsSb Avalanche Photodiode With a Small Temperature Coefficient of Breakdown

Dark current and avalanche gain M on AlAs0.56Sb0.44 (hereafter referred to as AlAsSb) separate absorption multiplication (SAM) avalanche photodiodes (APDs) were measured at temperatures ranging from 77 K to 300 K. To avoid possible ambiguity in breakdown voltage due to edge breakdown and tunneling current, a phase-sensitive detection method with a tightly focused light spot in the center of the device was employed to measure M accurately. An extrapolation of 1/M to zero was used to deduce the breakdown voltage, from which the temperature coefficient of breakdown voltage Cbd was derived. The value of Cbd 1/4 8 mV/K, obtained for AlAsSb SAM APDs, is much smaller than that for commercial Si and InGaAs/InP APDs, as well as other SAM APDs in the literature, demonstrating the potential of AlAsSb avalanche regions in improving the thermal stability of APDs.

Instantaneous Receiver Operating Characteristic (ROC) Performance of Multi-Gain-Stage APD Photoreceivers

We describe the use of analytical and numerical models of a multi-gain-stage single-carrier multiplication (SCM) avalanche photodiode (APD) to generate time-resolved receiver operating-characteristic (ROC) curves. First, pseudo-DC analytic models of discrete multi-stage APDs are used to generate the statistical properties of the SCM APD necessary for ROC analysis. Next, numerical models are used to develop the joint probability density function (PDF) of the SCM APD gain and avalanche buildup time as a function of the device structure, material properties and local electric fields. The instantaneous (time-resolved) carrier count distributions resulting from photon- and dark-initiated impact ionization chains are used to calculate the mean and variance of the currents induced in the circuits of the photoreceiver over the integration times of the detection event. Last, autocorrelation functions are generated to allow the parameters of the signal, the noise and the signal embedded in noise-which are necessary for ROC hypothesis testing-to be calculated for the instances of the impulse response. It is shown that time-resolved ROC analysis of an APD photoreceiver, which includes the instantaneous properties of photon- and dark-initiated avalanche events, allows for better optimization of photoreceiver performance than does non-time-resolved ROC analysis.

Electrical modeling of InSb PiN photodiode for avalanche operation

Current density-voltage (J-V) characteristics at 77 K of InSb pin photodiodes, in dark condition and under illumination, were simulated in view to design an avalanche photodiode (APD). Theoretical J-V results were compared with experimental results, performed on InSb diode fabricated by molecular beam epitaxy, in order to validate the parameter values used for the modeling. Then, with the assumption of multiplication induced by the electrons, an optimized separate absorption and multiplication APD structure was defined by theoretically studying the absorber doping level and the multiplication layer thickness. Calculated gain value higher than 10 was achieved at V = −4.5 V. This result shows the potentiality of InSb material as APD device.

SAGCM avalanche photodiode with additional layer and nonuniform electric field

This paper presents a new method to increase the speed of the separated absorption, grading, charge, and multiplication avalanche photodiode (SAGCM-APD). This improvement is obtained by adding a new thin charge layer between absorption and grading layers, with assuming the non-uniform electric field in different regions of the structure. In addition, a circuit model of the proposed structure is extracted, using carrier rate equations. Also, to achieve the optimum structure, it is tried to have trade-offs among thickness of the layers and have proper tuning of physical parameters. Eventually, frequency and transient response are investigated and it is shown that, in comparison with the previous conventional structure, significant improvements in gain-bandwidth product, speed and also in breakdown voltage are attained.

Discrimination of Photon- and Dark-Initiated Signals in Multiple Gain Stage APD Photoreceivers

We demonstrate the ability of linear mode single carrier multiplication (SCM) avalanche photodiode (APD)-based optical receivers to discriminate single-photon-initiated avalanche events from dark-current-initiated events. Because of their random spatial origin in discrete regions of the depletion region, in the SCM APD the dark-generated carriers multiply differently than the photon-generated carriers. This causes different count distributions and necessitates different statistical descriptions of the signal contributions from photon- and dark-originating impulse responses. To include dark carriers in the performance models of the SCM APD, we considered the influence of the spatial origin of the ionization chains on a receiver's noise performance over the times the optical pulse is integrated by the receiver's decision circuits. We compare instantaneous (time-resolved) numeric and pseudo-DC analytical models to measured SCM APD data. It is shown that it is necessary to consider both the distribution of spatial origin and the instantaneous properties of the ionization chains to describe statistically an SCM APD receiver. The ability of SCM APD receivers to discriminate single photon events from single dark events is demonstrated, and the effective gain and excess noise contributions of the light- and dark-initiated avalanche events and their influence on receiver sensitivity and signal-to-noise characteristics are shown.

Time resolved gain and excess noise properties of InGaAs/InAlAs avalanche photodiodes with cascaded discrete gain layer multiplication regions

To predict pulse detection performance when implemented in high speed photoreceivers, temporally resolved measurements of a 10-stage InAlAs/InGaAs single carrier multiplication (SCM) avalanche photodiode (APD)'s avalanche response to short multi-photon laser pulses were explained using instantaneous (time resolved) pulse height statistics of the device's impulse response. Numeric models of the junction carrier populations as a function of the time following injection of a primary photo-electron were used to create the probability density functions (pdfs) of the instances of the avalanche buildup process. The numeric pdfs were used to generate low frequency gain and excess noise models, which were in good agreement with analytic models of multiple discrete low-gain-stage APDs and with measured excess noise data. The numeric models were then used to generate the instantaneous and cumulative instantaneous low order statistics of the instances of the impulse response. It is shown that during the early times of the impulse response, the SCM APDs have lower excess noise than the pseudo-DC measurements and the common APD models used to describe them. The methods of determining the time resolved low order statistics of APDs are described and the importance of using time-resolved models of APD gain and noise is discussed.

P-type interface charge control layers for enabling GaN/SiC separate absorption and multiplication avalanche photodiodes

A p-type interface charge control layer (PICCL) is introduced that enables optimization of the net positive polarization induced interface charge at the GaN/SiC interface in GaN/SiC separate absorption and multiplication avalanche photodiodes (SAM-APDs) by varying its thickness. The response from SAM-APDs with PICCL thickness less than 10 nm has an anomalous shape at all bias attributed to the collection of carriers generated directly in the SiC layer. Devices with a 15 nm thick PICCL exhibit GaN related response at high bias that is indicative of punch-through of the electric field into the GaN absorption region due to optimization of the net interface charge.

The experimental investigation on dark current for InGaAs–InP avalanche photodiodes

To meet the requirement of photon-starved detection, separate absorption grading charge multiplication avalanche photodiodes (SAGCM APDs) have drawn more and more attentions. In this work, we presents a detailed analysis of dark currents for planar-type SAGCM InGaAs-InP APDs with different sub-micron thicknesses of multiplication layer, considering the effect of the diffusion process, generation-recombination process and tunneling process. According to our knowledge, it is the first time clearly demonstrating that the dominant component of dark current for a SAGCM APD changes with multiplication gain from surface to volume contribution. Our finding could be beneficial to the optimization of an APD with a SAGCM structure. An optimal InGaAs-InP APD with low-voltage operation (<40V) in combination with ultra-low dark current (0.10nA@M=8) has been demonstrated.

Effects of Dead Space on Avalanche Gain Distribution of X-Ray Avalanche Photodiodes

A random path length model for X-ray avalanche photodiodes (APDs) has been used to assess the effects of carriers' dead spaces and injection position on the avalanche gain distributions. Significant carrier's dead space, typically found in submicrometer avalanche regions, is found to reduce spread in the avalanche gain distribution, which is consistent with the reduced excess noise factors observed in conventional APDs. Mixed carrier-type injection increases the spread in the gain distribution along the avalanche region. The model was validated by comparing the results with experimental X-ray spectra from a GaAs/ Al0.8Ga0.2As separate absorption and multiplication APD. Good agreement was achieved between measured and simulated data. Avalanche multiplication shifted the detected photo peak away from the system noise, thereby improving its energy resolution and signal-to-noise ratio.

Development of a scintillation detector using a MPPC as an alternative to an APD

We conducted a study to examine the performance of the multi-pixel photon counter(MPPC). The MPPC is a novel type of semiconductor photodetector consisting of multiple avalanche photodiode (APD) pixels operated in Geiger mode. Whereas the MPPC offers a great advantage in signal multiplication comparable to that achieved by the photomultiplier tube (PMT), the detection of weak scintillation light signals is difficult due to the severe contamination of dark counts. In this study, we first compared the energy resolutions and energy thresholds of a 3 × 3 mm2 MPPC with those of a 3 × 3 mm2 APD as scintillation detectors. The MPPC and APD were optically coupled with 5 × 5 × 5 mm3 scintillation crystals of BGO, Tl:CsI, Pr:LuAG, and YAG. It turned out that the APD had better energy resolutions for 662 keV gamma-rays, while the MPPC had lower energy thresholds as measured using a test pulse. Despite the low energy thresholds, it is difficult for the MPPC to detect low energy gamma-rays due to the contamination of dark counts. Secondly, we applied a coincidence technique to discriminate weak gamma-ray signals from dark counts by using scintillation detectors that consisted of a 2 × 2 MPPC-array optically coupled with 10 × 10 × 10 mm3 crystals of GSO, BGO, and Pr:LuAG. With this technique, we demonstrated that dark counts achieved a rejection efficiency of more than 99.8%. As a result, 22.2 keV gamma-rays were successfully detected with a GSO scintillator as measured at +20°C.

Low Noise Avalanche Photodiodes Incorporating a 40 nm AlAsSb Avalanche Region

A separate absorption and multiplication avalanche photodiode incorporating a 500 nm InGaAs absorption layer, InAlAs bandgap grading/field control layers, an AlAsSb field control layer and a 40 nm AlAsSb multiplication layer was grown and characterized. Responsivity of 436 mA/W was measured at the punch-through voltage. A deviation of Be doping concentration in our AlAsSb field control layer leads higher than intended electric fields in the InGaAs absorption layer and the InAlAs field control layer. Calculation of avalanche gain suggests that the gain in the InGaAs is low and therefore the gain and excess noise characteristics are dominated by impact ionization in the InAlAs field control layer and the AlAsSb multiplication layer. Despite this low excess noise factors corresponding to an effective electron to hole ionization coefficient ratio between 0.1 to 0.15, were measured. This is lower than that from an InAlAs pin diode with a 100 nm avalanche region.

Effect of Interface Polarization Charge on GaN/SiC Separate Absorption and Multiplication Avalanche Photodiodes

A III-Nitride/ SiC separate absorption and multiplication avalanche photodiode (SAM-APD) offers a novel approach for fabricating high gain photodetectors with tunable absorption over a wide spectrum from the visible to deep ultraviolet. However, unlike conventional heterojunction SAM APDs, the formation of polarization-induced charge at the hetero-interface arising from spontaneous and piezoelectric polarization can dramatically affect the performance of this detector. In this paper we report on the role of this interface charge on the performance of GaN/SiC SAM APDs.

GaN/SiC avalanche photodiodes

Near ultraviolet-sensitive separate absorption and multiplication avalanche photodiodes with GaN/SiC epitaxial layers grown on SiC substrate were fabricated. Dark current &amp;lt; 1 pA at 90% breakdown voltage, maximum multiplication gain of ∼105, and responsivity exceeding 4.2 A/W at 365 nm were achieved.

Improvement of Energy Thresholds for Scintillation Detectors Using a Monolithic 2 ×2 Multi-Pixel Photon Counter Array with a Coincidence Technique

The performance of a large-area, monolithic Hamamatsu multi-pixel photon counter (MPPC) was tested consisting of a 2 ×2 array of 3 ×3 mm 2 pixels. MPPC is a novel type of semiconductor photodetector comprising multiple avalanche photodiode (APD) pixels operated in Geiger mode. Despite its great advantage of signal multiplication comparable to that achieved with the photomultiplier tube (PMT), the detection of weak scintillation light signals is quite difficult due to the severe contamination of dark counts, which typically amounts to ≃1 Mcps/3 ×3 mm 2 at room temperature. In this study, a coincidence technique was applied for scintillation detectors to improve the detection efficiency for low energy gamma-rays. The detector consisted of a 10 ×10 ×10 mm 3 crystals of GSO, BGO, and Pr:LuAG optically coupled with the 2 ×2 MPPC-array. With this technique, we demonstrated that the contamination of dark counts was reduced with a rejection efficiency of more than 99.8%. As a result, 22.2 keV gamma-rays were succ...

III-NITRIDE/SiC SEPARATE ABSORPTION AND MULTIPLICATION AVALANCHE PHOTODIODES: THE IMPORTANCE OF CONTROLLING POLARIZATION-INDUCED INTERFACE CHARGE

A III-Nitride/ SiC separate absorption and multiplication avalanche photodiode (SAM-APD) offers a novel approach for fabricating high gain photodetectors with tunable absorption over a wide spectrum from the visible to deep ulltraviolet. However, unlike conventional heterojunction SAM APDs, the formation of polarization-induced charge at the hetero-interface arising from spontaneous and piezoelectric polarization can dramatically affect the performance of this detector. In this paper we report on the role of this interface charge on the performance of GaN / SiC SAM APDs. Simulations of the electric field profile within this device structure while biased near avalanche breakdown indicate that the density of positive interface charge may be sufficient to confine the electric field within the SiC multiplication region with negligible punch-through into the GaN absorption region, a distribution that is likely undesirable for efficient collection of photo-generated holes due to the presence of defects at the hetero-interface. Simulations further show that the incorporation of a p -type doped interface charge control layer at the hetero-interface can modify the total density of charge at the interface and allow for the tailoring of the electric field profile within this device. Experimental results are provided that correlate well with the simulation results.

Modeling the Effects of Interface Traps on the Static and Dynamic Characteristics of Ge/Si Avalanche Photodiodes

The influence of interface donor and acceptor traps on the static and dynamic behavior of Ge/Si separate absorption, charge, and multiplication avalanche photodiodes (APDs) is modeled. The effects of different trap types, densities, and carrier capture cross sections on the dark current level, breakdown voltage, dc gain, and electric field profile, as well as on the frequency response and gain-bandwidth product of the device, are investigated for the first time. Our results show that the interface traps significantly increase the dark current and reduce the gain from 290 to less than 10. We also show that the acceptor traps reduce the APD bandwidth considerably to 0.5 GHz whereas the donor traps increase the bandwidth to around 10 GHz.