雪崩光电二极管(APD)PPT课件
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The Multiplication Process
Measured values of ionisation coefficients e and h for some
common semiconductor materials, plotted versus (1/E).
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9
The Multiplication Process
We may define ionisation coefficients for electrons and holes, e and h respectively, as the probability that a given carrier will excite an electron-hole pair in unit distance. The coefficients increase so rapidly with increasing electric field strength, that it is often convenient to think in terms of a breakdown field, EB, at which avalanche excitation becomes critical, say becomes of the order 105 – 106 m-1. Graphs of e and h versus electric field are plotted for a number of semiconductors known to be of interest as detector materials. The curves refer to room temperature. As the temperature increases, the ionisation coefficients decrease, because the greater number of scattering collisions reduces the high-energy tail of the carrier energy distribution and hence reduces the probability of excitation. In some materials e >h, in others h>e, while in gallium arsenide and indium phosphide the two coefficients are approximately the same. The ratio
The first is the series resistance of the bulk semiconductor, RS, between the junction and the diode terminals. The second is the effect of the rise in temperature resulting from the increased dissipation as the current rises. This reduces the values of e and h and raises the breakdown voltage. It also increases the rate of thermal generation of carriers and hence the dark current. Multiplication factors measured as a function of the applied terminal voltage, V, can usually be fitted to the form
雪崩光电二极管 （APD）探测器
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Avalanche Photodiode Detectors
The Multiplication Process Avalanche Photodiode Designs Avalanche Photodiode Bandwidth Avalanche Photodiode Noise
ຫໍສະໝຸດ Baidu
k = h/e
is found to lie in the range 0.01 to 100.
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The Multiplication Process - Experimental Behaviour
Two factors limit the increase of Me, the multiplication factor for the injected electrons and hence I as the applied voltage approaches the breakdown voltage, VB, at which the values e and h satisfy the condition for breakdown, that is M->.
M = 1 / |1-(V-IR’)/VB|n
Where R’ = RS +RTh is the sum of the series resistance, RS, and an effective resistance, RTh, which derives from the rise in temperature. The index, n, is a function of the detailed design and the material of the diode. Some typical 11 curves of M(V) for a silicon APD are shown in the figure.
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The Multiplication Process
Measured values of ionisation coefficients e and h for some
common semiconductor materials, plotted versus (1/E).
12
13
14
9
The Multiplication Process
We may define ionisation coefficients for electrons and holes, e and h respectively, as the probability that a given carrier will excite an electron-hole pair in unit distance. The coefficients increase so rapidly with increasing electric field strength, that it is often convenient to think in terms of a breakdown field, EB, at which avalanche excitation becomes critical, say becomes of the order 105 – 106 m-1. Graphs of e and h versus electric field are plotted for a number of semiconductors known to be of interest as detector materials. The curves refer to room temperature. As the temperature increases, the ionisation coefficients decrease, because the greater number of scattering collisions reduces the high-energy tail of the carrier energy distribution and hence reduces the probability of excitation. In some materials e >h, in others h>e, while in gallium arsenide and indium phosphide the two coefficients are approximately the same. The ratio
The first is the series resistance of the bulk semiconductor, RS, between the junction and the diode terminals. The second is the effect of the rise in temperature resulting from the increased dissipation as the current rises. This reduces the values of e and h and raises the breakdown voltage. It also increases the rate of thermal generation of carriers and hence the dark current. Multiplication factors measured as a function of the applied terminal voltage, V, can usually be fitted to the form
雪崩光电二极管 （APD）探测器
1
Avalanche Photodiode Detectors
The Multiplication Process Avalanche Photodiode Designs Avalanche Photodiode Bandwidth Avalanche Photodiode Noise
ຫໍສະໝຸດ Baidu
k = h/e
is found to lie in the range 0.01 to 100.
10
The Multiplication Process - Experimental Behaviour
Two factors limit the increase of Me, the multiplication factor for the injected electrons and hence I as the applied voltage approaches the breakdown voltage, VB, at which the values e and h satisfy the condition for breakdown, that is M->.
M = 1 / |1-(V-IR’)/VB|n
Where R’ = RS +RTh is the sum of the series resistance, RS, and an effective resistance, RTh, which derives from the rise in temperature. The index, n, is a function of the detailed design and the material of the diode. Some typical 11 curves of M(V) for a silicon APD are shown in the figure.