There is an increased demand for low noise avalanche photodiodes (APDs) for infrared wavelengths at 1550 nm for long range Light Detection and Ranging applications. Here we present two classes of APD that produce high avalanche gain but with extremely low excess noise factors, F ~ 2. InAs APDs show F < 2 and offer detection wavelength up to 3500 nm, although this drops to ~3000 nm when cooled. For reducing effects of scattering in atmosphere, InAs could be an attractive option. In addition InAs APDs are based on a simple homojunction design, which is relatively easy to grow epitaxially. AlGaAsSb when combined with InGaAs, provides a direct replacement for the traditional InGaAs/InP APDs. It is therefore capable of room temperature performance with excess noise performance similar to Si APDs but operates at 1550 nm. We will present results that show noise equivalent power as low as 69 fW/Hz0.5.
In this paper, we report the temperature stability and robust performance of our avalanche photodiode (APD), as well as the wide dynamic range and high gain linear mode detection ability of our receiver module prototype. The APDs have a low dark current and low-temperature coefficient of operating voltages from 19.2 to 22.7 mV/°C with a gain from 10 to 200. The high sensitivity APD- transimpedance amplifier (TIA) receiver module (TIA gain 22 kV/A) demonstrates measured NEP value of 29 fW/Hz0.5 when APD operates @M=130 under room temperature and predicted NEP value of 18 fW/Hz0.5@M=200 under 0°C for the 180 MHz of measurement bandwidth. This corresponds to a detection level of 16 and 10 photons respectively. The NEP value under 85°C is predicted as 77 fW/Hz0.5 when APD operates @M=60. This receiver module has a fast overload recovery of 1.39 μs under 51 kW/cm2 optical power illumination with 1045 kV/W of overall responsivity for APD-TIA. Our APDs also show robust performance of optically induced damage threshold of 40 MW/cm2 optical power illumination under circuitry protection and power dissipation limit of ~190 mW without circuitry protection.
It is well known that avalanche photodiode can enhance the signal to noise ratio of a detection system, when the excess avalanche noise is low. The excess noise factor, F which characterizes the excess noise of an APD can be calculated using the established noise theory from R. McIntyre. When the ratio of hole to electron ionization coefficients, k = 0, F ~2 is achieved at high gain. This means the avalanche gain, M, can be increased without the penalty of increased excess noise factor. In this work, we will present the progress in APDs incorporating InAs and AlGaAsSb as the avalanche regions. Both show k ~0 and therefore F~2. The former can be used for low photon detection at wavelengths beyond InGaAs, while the latter can be combined with InGaAs to provide low noise APD for wavelengths up to 1700 nm. Our work demonstrated that low photons of < 100 photon within a 50 microsecond pulse can be detected using InAs APDs. We also achieved single photon detection at 1550 nm using AlGaAsSb APD.
Avalanche photodiodes (APD) can improve the signal to noise ratio in applications such as LIDAR, range finding and optical time domain reflectometry. However, APDs operating at eye-safe wavelengths around 1550 nm currently limit the sensitivity because the APDs’ impact ionization coefficients in the avalanche layers are too similar, leading to poor excess noise performance. The material AlGaAsSb has highly dissimilar impact ionization coefficients (with electrons dominating the avalanche gain) so is an excellent avalanche material for 1550 nm wavelength APDs. We previously reported a 1550 nm wavelength AlGaAsSb SAM APD with extremely low excess noise factors, 1.93 at a gain of 10 and 2.94 at a gain of 20. Using a more optimized design, we have now realized an AlGaAsSb SAM APD with a lower dark current (7 nA at a gain of 10 from a 230 μm diameter APD), a higher responsivity (0.97 A/W) and a lower excess noise (1.9 at a gain of 40), compared to our previous SAM APD. Noise-equivalent-power (NEP) measurements of our APD with a simple transimpedance amplifier circuit produced an NEP 12 times lower than a state-of-the-art APD under identical test conditions, confirming the advantage of low-noise AlGaAsSb SAM APDs.
The optical detector used in pulsed LIDAR, range finding and optical time domain reflectometry systems is typically the limiting factor in the system’s sensitivity. It is well-known that an avalanche photodiode (APD) can be used to improve the signal to noise ratio over a PIN detector, however, APDs operating at the eye-safe wavelengths around 1550 nm are limited in sensitivity by high excess noise. The underlying issue is that the impact ionization coefficient of InAlAs and InP used as the avalanche region in current commercial APDs are very similar at high gain, leading to poor excess noise performance. Recently, we have demonstrated extremely low noise from an Al(Ga)AsSb PIN diode with highly dissimilar impact ionization coefficients due to electron dominated impact ionization. In this paper, we report on the first low noise InGaAs/AlGaAsSb separate absorption, grading and multiplication APDs operating at 1550 nm with extremely low excess noise factor of 1.93 at a gain of 10 and 2.94 at a gain of 20. Furthermore, the APD’s dark current density was measured to be 74.6 μA/cm2 at a gain of 10 which is competitive with commercial devices. We discuss the impact of the excess noise, dark current and responsivity on the APDs sensitivity and, project a noise-equivalent power (NEP) below 80 fW/Hz0.5 from a 230 μm diameter APD and commercial transimpedance amplifier (TIA). The prospects for the next generation of extremely low noise APDs for 1550 nm light detection are discussed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.