Application of Keithley Picoammeter in Reverse Current Measurement of Avalanche Photodiode

Picoammeter is designed and produced according to the actual needs of various industrial sites. It has a wide range of applications, such as measuring the resistance (rate) of insulating materials, dark current measurement of photodiodes, measurement of bioelectric current, etc. Keithley picoammeter is the first choice of many customers. Today, Antai Testing will share with you the application of Keithley picoammeter in reverse current measurement of avalanche photodiodes.

Avalanche Photodiode Overview:

Avalanche photodiode (APD) is a high-sensitivity, high-speed photodiode. When reverse voltage is applied, its internal gain mechanism can be activated. The gain of APD can be controlled by the amplitude of reverse bias voltage. The greater the reverse bias voltage, the higher the gain. APD works under the action of electric field strength, and the avalanche multiplication of photocurrent is similar to a chain reaction. APD is used in various applications that require high sensitivity to optical signals, such as fiber optic communication, scintillation detection, etc.

The measurements of APDs generally include breakdown voltage, responsivity, and reverse bias current. The maximum rated current of a typical APD is 10-4 to 10-2A, while its dark current can be as low as 10-12 to 10-13A. The maximum reverse bias voltage varies with the material of the APD, ranging from 100V for devices made of indium gallium arsenide (InGaAs) to 500V for devices made of silicon.

Test description:

Measuring the reverse bias current of an APD requires an instrument that can measure current over a wide range and output a swept voltage. Because of this requirement, instruments such as the Keithley Picoammeter Model 6487 Voltage Source or Model 6430 Sub-Femtoamp Source-Meter are ideal for this type of measurement.

Figure 1. APD connection to Keithley Picoammeter 6430

Figure 2. Relationship between current and reverse scan voltage of InGaAs APD

Keithley Picoammeter Product Advantages:

It can measure ultra-low leakage currents in components, dark currents in optical devices, and beam currents in microscopy instruments.

High-precision current measurements can be made, even in circuits with very low source voltages.

Simplifies the process of analyzing multi-channel devices, monitoring current at multiple locations on a material, and recording data from multiple sensors at once.

Make sure you can find the voltage bias function that suits your application requirements. Perform insulation resistance testing with a 500V source in the Model 6487 Picoammeter/Voltage Source.

Allows measurement results to be transferred to a device such as a digital multimeter, data acquisition card, oscilloscope, or strip chart recorder for signal response and trend analysis.

Supports measurement of high current, such as measuring 4-20mA sensor loop.

Supports high-throughput production testing needs.

Simplifies synchronization with other instruments and voltage sources by combining six independently selectable trigger lines on a single connector for simple, direct control of all instruments in the system.