TECHNICAL FIELD

Embodiments of this disclosure relate generally to photodiodes.

BACKGROUND

The function of a photodetector is to sense incident light and to output an electrical current, the photocurrent, proportional to the incident light flux. Ideally, the photodetector produces one output electron or hole for every incident photon and every output electron or hole is the result of an incident photon. For many applications where the incident flux is low, the output current requires amplification before it can be used by subsequent electronics. In some previous photodetectors, in order to achieve photon counting, then a gain mechanism for multiplying the photocurrent by 104to 106is needed to detect a single photon. Besides increasing the amplitude of the current, amplifiers have the drawback of adding noise to the current.

Practically, the noise current from electronic amplifiers at room temperature for many types of photodetectors is well above that required for detecting a stream of single photons (photon counting). Since the amplifier noise is temperature-driven, for these type of photodetectors, then cooling the amplifier to cryogenic temperatures would lower its noise but this approach is acceptable only for a limited number of applications.

One current multiplication mechanism is impact ionization. Photodetectors based on this mechanism are known as avalanche photodiodes (APDs).

SUMMARY

Provided herein can be various methods, apparatuses, and systems for photodiodes.

In an embodiment, a photodiode, such as a linear mode avalanche photodiode can be made free of excess noise via having a superlattice multiplication region that allows only one electrical current carrier type, such as an electron or a hole, to accumulate enough kinetic energy to impact ionize when biased, where the layers are lattice matched. A photodiode can be constructed with i) a lattice matched pair of a first semiconductor alloy and a second semiconductor alloy in a superlattice multiplication region, ii) an absorber region, and iii) a semiconductor substrate. A detector with multiple photodiodes can be made with these construction layers in order to have a cutoff wavelength varied anywhere from 1.7 to 4.9 μm as well as a noise resulting from a dark current at a level such that an electromagnetic radiation signal with the desired minimum wavelength cutoff can be accurately sensed by the photodiode.

A photodiode can be constructed with i) a lattice matched pair of a first semiconductor alloy and a second semiconductor alloy in a superlattice multiplication region, ii) an absorber region, and iii) a semiconductor substrate. The absorber region can also have a superlattice construction of multiple semiconductor alloys. A given photodiode can be constructed with a lattice matched pair of a first semiconductor alloy and a second semiconductor alloy in a superlattice multiplication region that allows only one electrical-current carrier type selected from i) an electron or ii) a hole to accumulate enough kinetic energy to impact ionize when the photodiode is electrically biased to conduct electrical current. The photodiode will have a third semiconductor alloy forming an absorber region and a semiconductor substrate. The multiplication region and absorber region can be lattice matched to the semiconductor substrate. The multiplication region and the absorber region alternatively stack upon each other starting from the semiconductor substrate.

The alloys in the multiplication region, the absorber region, and the semiconductor substrate are matched to provide the photodiode to have a minimum wavelength cutoff between 1.0 μm and 4.9 μm as well as a noise resulting from a dark current at a level such that an electromagnetic radiation signal with the desired minimum wavelength cutoff can be accurately sensed by the photodiode.

Many variations of this design will be discussed.

