InP Multiplication Layer Research Articles

Structural design of dual carrier multiplication avalanche photodiodes on InP substrate

Avalanche photodiodes are widely used in various fields, such as optical communication and laser radar, because of their high multiplication. In order to adapt to very weak signal detection applications, devices are required to have higher gain values. The existing avalanche photodiodes generally use single carrier multiplication mode of operation, its multiplication effect is limited. In this paper is designed an InP/In<sub>0.53</sub>Ga<sub>0.47</sub>As/In<sub>0.52</sub>Al<sub>0.48</sub>As avalanche photodiode structure with electrons and holes jointly involved in multiplication. In this structure, In<sub>0.53</sub>Ga<sub>0.47</sub>As material is used for the absorption layer, InP material is used for the hole multiplication layer, In<sub>0.52</sub>Al<sub>0.48</sub>As is used for the electron multiplication layer, and the two multiplication layers are distributed on the upper side and lower side of the absorber layer. Under the reverse bias, the photogenerated electrons and the absorber-layer generated holes can enter into the respective multiplier layers in different directions and create the avalanche multiplication effect, so that the carriers are fully utilized. This structure and the conventional single multiplication layer structure are simulated by Silvaco TCAD software. Comparing the single InP multiplication layer structure with the single In<sub>0.52</sub>Al<sub>0.48</sub>As multiplication layer structure, the gain value of the double multiplication layer structure at 95% breakdown voltage is about 2.3 times and about 2 times of the former two, respectively, and the device has a larger gain value because both carriers are involved in multiplication in both multiplication layers at the same time. The structure has a dark current of 1.5 nA at 95% breakdown voltage, which does not increase in comparison with the single multiplication layer structure, owing to the effective control of the electric field inside the structure by multiple charge layers. Therefore, this structure is expected to improve the detection sensitivity of the system.

A comparative study of front- and back-illuminated planar InGaAs/InP avalanche photodiodes

In this work, a planar In0.53Ga0.47As/InP avalanche photodiode (APD) working in both front- and back-illumination modes is fabricated for a comparative study. The great differences in the electrical and spectral performances between the two operating approaches can be originated from the PIN junction in the InP cap layer with high electric field, which plays the role of short-wavelength photoelectric conversion before the InP multiplication layer punches through under front-illumination.

Origin of large dark current increase in InGaAs/InP avalanche photodiode

The large dark current increase near the breakdown voltage of an InGaAs/InP avalanche photodiode is observed and analyzed from the aspect of bulk defects in the device materials. The trap level information is extracted from the temperature-dependent electrical characteristics of the device and the low temperature photoluminescence spectrum of the materials. Simulation results with the extracted trap level taken into consideration show that the trap is in the InP multiplication layer and the trap assisted tunneling current induced by the trap is the main cause of the large dark current increase with the bias from the punch-through voltage to 95% breakdown voltage.

Dependence of dark current on carrier lifetime for InGaAs/InP avalanche photodiodes

Effects of carrier lifetime of all layers on the dark current have been studied for the separate-absorption-grading-charge-multiplication InGaAs/InP avalanche photodiodes (APDs). The results indicate that the remarkably increasing of the dark current at the punch-through voltage strongly depends on the carrier lifetime of InGaAs absorption layer. According to the simulation results, we can estimate the carrier lifetime of InGaAs absorption layer and InP multiplication layer to be about 100 ns and 20 ps for our fabricated device. And we can see that the dark current of APDs near the breakdown voltage is mainly dominated by the thermal generation–recombination current from the InGaAs absorption layer and trap-assisted-tunneling current from the InP multiplication layer.

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.

Modeling of two-dimensional gain profiles for InP-InGaAs avalanche photodiodes with a stochastic approach

The two-dimensional (2-D) gain profiles for separate absorption, grading, charge and multiplication (SAGCM) InP-InGaAs avalanche photodiodes (APD's) have been modeled with a stochastic approach. To consider the influence of the curved diffusion edge on the electric field within the periphery region, equations are derived from the cylindrical Poisson's equation. The electric field profiles are computed at various APD radii and the electric field in the multiplication layer is reduced significantly for APD's with a partial charge sheet in the periphery. It is demonstrated by the modeled 2-D gain profiles that the premature edge breakdown can be effectively suppressed for such devices. The modeled 2-D gain profiles for APD's with a partial charge sheet incorporated in the periphery are in good agreement with the experimental results. The results and the uniformity issue of the 2-D gain profiles are discussed. The effect of using curved diffusion interfaces instead of a steep mesa step is also explored; this suggests that the fabrication of a charge sheet mesa step may complicate the gain uniformity issue. From our analyses, we find that the uncertainty and the symmetry of both patterning the charge sheet mesa structure and controlling the diffusion interface between the p/sup +/ InP top layer and the n/sup -/ InP multiplication layer are most likely to affect the uniformity and the symmetry of the 2-D gain profiles for the SAGCM InP-InGaAs APD's.

Fabrication of InGaAs/InP avalanche photodiodes by reactive ion etching using CH4/H2 gases

In this article, the first successful application of CH4/H2 reactive ion etching (RIE) techniques to the fabrication of an InGaAs/InP avalanche photodiode (APD) with very low dark current is reported. A partial charge sheet layer in the device periphery prepared by the CH4/H2 RIE was used for the fine control of electric field. On the top of the dry-etched partial charge sheet layer and charge plate layer, an n−-InP multiplication layer was grown by metalorganic chemical vapor deposition. Very low dark current less than 1 nA at 90% of breakdown voltage was obtained, indicating the minimal RIE-induced damages. The CH4/H2 RIE was shown to be applicable to devices operating under high electric field, such as APD’s.

High-performance avalanche photodiode with separate absorption ‘grading’ and multiplication regions

High-speed operation of avalanche photodiodes with separated absorption and multiplication regions has been achieved by incorporating an intermediate bandgap InGaAsP ‘grading’ layer between the InP multiplication layer and the InGaAs absorption layer. These APDs also exhibit low dark currents, high quantum efficiencies and good avalanche gains. Sensitivity measurements have been made at 1.3 μm and 1.55 μm with one of these APDs in a high-speed optical receiver: at bit rates of 420 Mbit/s and 1 Gbit/s the minimum average powers required for 10−9 BER are −43 dBm and −38 dBm at 1.55 μm, and −41.5 dBm and −37.5 dBm at 1.3 μm, respectively.