Carrier Lifetime
Encyclopedia
A definition in semiconductor physics, carrier lifetime is defined as the average time it takes for a minority carrier to recombine
. The process through which this is done is typically known as minority carrier recombination.
The energy released due to recombination
can be either thermal, thereby heating up the semiconductor (thermal recombination or non-radiative recombination
, one of the sources of waste heat
in semiconductor
s), or released as photon
s (optical recombination, used in LEDs
and semiconductor lasers).
Carrier lifetime plays an important role in bipolar transistors
and solar cells.
, carrier lifetime is used in the charge conservation equation as the time constant of the exponential decay of carriers.
The dependence of carrier lifetime on the carrier density is expressed as:
where A, B and C are the non-radiative, radiative and Auger recombination coefficients and
is the carrier lifetime.
Carrier generation and recombination
In the solid state physics of semiconductors, carrier generation and recombination are processes by which mobile charge carriers are created and eliminated. Carrier generation and recombination processes are fundamental to the operation of many optoelectronic semiconductor devices, such as...
. The process through which this is done is typically known as minority carrier recombination.
The energy released due to recombination
Carrier generation and recombination
In the solid state physics of semiconductors, carrier generation and recombination are processes by which mobile charge carriers are created and eliminated. Carrier generation and recombination processes are fundamental to the operation of many optoelectronic semiconductor devices, such as...
can be either thermal, thereby heating up the semiconductor (thermal recombination or non-radiative recombination
Non-radiative recombination
Non-radiative recombination is a process in phosphors and semiconductors, whereby charge carriers recombine without releasing photons. A phonon is released instead....
, one of the sources of waste heat
Waste heat
Waste heat sometimes called Secondary heat or Low-grade heat refers to heat produced by machines, electrical equipment and industrial processes for which no useful application is found. Energy is often produced by a heat engine, running on a source of high-temperature heat...
in semiconductor
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...
s), or released as photon
Photon
In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
s (optical recombination, used in LEDs
Light-emitting diode
A light-emitting diode is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting...
and semiconductor lasers).
Carrier lifetime plays an important role in bipolar transistors
Bipolar junction transistor
|- align = "center"| || PNP|- align = "center"| || NPNA bipolar transistor is a three-terminal electronic device constructed of doped semiconductor material and may be used in amplifying or switching applications. Bipolar transistors are so named because their operation involves both electrons...
and solar cells.
Carrier lifetime in semiconductor lasers
In semiconductor lasers, the carrier lifetime is the time it takes an electron before recombining via non-radiative processes in the laser cavity. In the frame of rate equations modelLaser diode rate equations
The laser diode rate equations model the electrical and optical performance of a laser diode. This system of ordinary differential equations relates the number or density of photons and charge carriers in the device to the injection current and to device and material parameters such as carrier...
, carrier lifetime is used in the charge conservation equation as the time constant of the exponential decay of carriers.
The dependence of carrier lifetime on the carrier density is expressed as:
where A, B and C are the non-radiative, radiative and Auger recombination coefficients and
is the carrier lifetime.