21.5 Applications and Special Diode Devices
583
Fig. 21.69 Current versus time trace for a (soft) fast-recovery diode. Reprinted with permission from [1795]
(a)
(b)
Fig. 21.70 a Current versus time trace for a step-recovery diode and sinusoidal voltage input. The lifetime must be
sufficiently large such that a current peak is reached. b Definition of the snapback time T s . Reprinted with permission
from [1796]
21.5.7 Step-Recovery Diodes
This type of diode is designed to store charge in the forward direction. If polarity is reversed, the charge
will allow conductance for a short while, ideally until a current peak is reached (Fig. 21.70a), and then
cutoff the current very rapidly during the so-called snapback time T s (Fig. 21.70b). The cutoff can be
quite rapid, in the ps regime. These properties are used for pulse (comb) generation or as a gate in fast
sampling oscilloscopes. In Si, only 0.5–5 µs are reached (fast-recovery diode, see previous section)
while GaAs diodes can be used in the several tens of GHz regime.
Using a heterostructure GaAs/AlGaAs diode (cf. Sect. 21.4.6), as shown schematically in Fig. 21.71a,
a steepening of a 15-V, 70-ps (10% to 90%) pulse to a fall time of 12 ps was observed (Fig. 21.71c).
The forward current of the diode was 40 mA, supplied via a bias tee.
21.5.8 Pin-Diodes
In a pin-diode, an intrinsic (i), i.e. undoped region (with higher resistivity) is located between the nand the p-regions. Often, also a region with low n- or p-doping is used. In this case, the center region is
denoted as a ν- or π -region, respectively. The fabrication of arbitrary doping profiles and an intrinsic
region poses little problem for epitaxial diodes.
583
Fig. 21.69 Current versus time trace for a (soft) fast-recovery diode. Reprinted with permission from [1795]
(a)
(b)
Fig. 21.70 a Current versus time trace for a step-recovery diode and sinusoidal voltage input. The lifetime must be
sufficiently large such that a current peak is reached. b Definition of the snapback time T s . Reprinted with permission
from [1796]
21.5.7 Step-Recovery Diodes
This type of diode is designed to store charge in the forward direction. If polarity is reversed, the charge
will allow conductance for a short while, ideally until a current peak is reached (Fig. 21.70a), and then
cutoff the current very rapidly during the so-called snapback time T s (Fig. 21.70b). The cutoff can be
quite rapid, in the ps regime. These properties are used for pulse (comb) generation or as a gate in fast
sampling oscilloscopes. In Si, only 0.5–5 µs are reached (fast-recovery diode, see previous section)
while GaAs diodes can be used in the several tens of GHz regime.
Using a heterostructure GaAs/AlGaAs diode (cf. Sect. 21.4.6), as shown schematically in Fig. 21.71a,
a steepening of a 15-V, 70-ps (10% to 90%) pulse to a fall time of 12 ps was observed (Fig. 21.71c).
The forward current of the diode was 40 mA, supplied via a bias tee.
21.5.8 Pin-Diodes
In a pin-diode, an intrinsic (i), i.e. undoped region (with higher resistivity) is located between the nand the p-regions. Often, also a region with low n- or p-doping is used. In this case, the center region is
denoted as a ν- or π -region, respectively. The fabrication of arbitrary doping profiles and an intrinsic
region poses little problem for epitaxial diodes.