Active solid-state devices (e.g. – transistors – solid-state diode – Voltage variable capacitance device
Reexamination Certificate
1999-05-26
2003-04-22
Eckert, George (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Voltage variable capacitance device
C257S015000, C257S017000
Reexamination Certificate
active
06552412
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device with a new structure.
2. Description of the Related Art
A diode has been known to have a pn or pin junction structure. With respect to a current-voltage characteristic of the diode, a characteristic that electric current increase when an applied voltage increases and a characteristic that electric current decrease when an applied voltage decreases show identical characteristics. Especially, the diode does not show a hysterisis characteristic in a current-voltage characteristic.
SUMMARY OF THE INVENTION
The inventors of the present invention formed a device having a quantum-wave interference layer which reflects quantum-waves and a middle layer which does not have a multi-period structure but has a plane structure in a band structure, where the quantum-wave interference layer and the middle layer are connected in series, and measured a current-voltage characteristic of the device. The current-voltage characteristic of the device shows that when an applied voltage increases in a forward direction, an electric current rises abruptly at a certain value of voltage with a step function. Also, the current-voltage characteristic of the device shows that when an applied voltage decreases in a backward direction from the region where the electric current increases first, the electric current decreases at a certain value of voltage, which is different from the value described above, with a step function. In short, a hysterisis characteristic that the device has different value of voltage when the electric current rises and decreases abruptly with a step function, or when the current-voltage characteristic varies with a step function can be found.
It is, therefore, an object of the present invention to provide a semiconductor device with a new structure using this hysterisis characteristic. The semiconductor device in the present invention utilizes a hysterisis of the current-voltage characteristic which varies with a step function, and can be applied to Schmitt circuit and a binary element. That is, the device which does not show chattering with respect to a condition variation can be provided.
In the light of these objects a first aspect of the present invention is a semiconductor device which is constituted by a quantum-wave interference layer units having plural periods of a pair of a first layer and a second layer, the second layer having a wider band gap than the first layer, and a middle layer disposed between adjacent two of the quantum-wave interference layer units. Each thickness of the first and the second layers is determined by multiplying by an odd number one fourth of a quantum-wave wavelength of carriers in each of the first and the second layers. Plural units of the quantum-wave interference layers are formed with a middle layer, which does not have a multi-period structure but has a plane band structure, lying between each of the quantum-wave interference units.
The second aspect of the present invention is to set a kinetic energy of the carriers, which determines the quantum-wave wavelength, at the level near the bottom of a conduction band when the carriers are electrons or at the level near the bottom of a valence band in the second layer when the carriers are holes.
The third aspect of the present invention is to define each thickness of the first and the second layers as follows:
D
W
=n
W
&lgr;
W
/4
=n
W
h
/4[2
m
W
(
E+V
]
½
(1)
and
D
B
=n
B
&lgr;B
/4
=n
B
h
/4(2
m
B
E
)
½
(2)
In Eqs. 1 and 2, h, m
W
, m
B
, E, V, and n
W
, n
B
represent Plank's constant, the effective mass of carrier conducting in the first layer, the effective mass of carriers in the second layer, the kinetic energy of the carriers at the level near the lowest energy level of the second layer, the potential energy of the second layer relative to the first layer, and odd numbers, respectively.
The fourth aspect of the present invention is a quantum-wave interference layer having a partial quantum-wave interference layers I
k
with arbitrary periods T
k
including a first layer having a thickness of n
Wk
&lgr;
Wk
/4 and a second layer having a thickness of n
Bk
&lgr;
Bk
/4 for each of a plural different values E
k
, E
k
+V. E
k
, E
k
+V, &lgr;
Bk
, &lgr;
Wk
, and n
Bk
, n
Wk
represent a kinetic energy of carriers conducted in the second layer, a kinetic energy of carriers conducted in the first layer, a quantum-wave wavelength corresponding energies of the second layer and the first layer, and odd numbers, respectively.
The fifth aspect of the present invention is to form a middle layer having narrower bandwidth than that of the second layer.
The sixth aspect of the present invention is to form a middle layer having half a thickness of its quantum-wave wavelength &lgr;
B
.
The seventh aspect of the present invention is to form a &dgr; layer between the first layer and the second layer, which sharply varies energy band at the boundary between the first and second layers and is substantially thinner than that of the first and the second layers.
The eighth aspect of the present invention is a semiconductor device having a pin junction structure, and the quantum-wave interference layer and the middle layer are formed in the i-layer.
The ninth aspect of the present invention is to form the quantum-wave interference layer and the middle layer in the n-layer or the p-layer.
The tenth aspect of the present invention is a semiconductor device having a hysterisis characteristic as a current-voltage characteristic.
First to Third, and Eighth to Tenth Aspects of the Invention
The principle of the semiconductor device of the present invention is explained hereinafter.
FIG. 1A
shows an energy diagram of a conduction band and a valence band when an external voltage is applied to the interval between the p-layer and the n-layer in a forward direction. As shown in
FIG. 1A
, the conduction band of the i-layer becomes plane by applying the external voltage. Four quantum-wave interference layer units Q
1
to Q
4
are formed in the i-layer, and middle layers C
1
to C
3
are formed at each intervals of the quantum-wave interference layer units.
FIG. 2
shows a conduction band of a quantum-wave interference layer unit Q
1
having a multi-layer structure with plural periods of a first layer W and a second layer B as a unit. A band gap of the second layer B is wider than that of the first layer W.
Electrons conduct from left to right as shown by an arrow in FIG.
2
. Among the electrons, those that exist at the level near the lowest energy level of a conduction band in the second layer B are most likely to contribute to conduction. The electrons near the bottom of conduction band of the second layer B has a kinetic energy E. Accordingly, the electrons in the first layer W have a kinetic energy E+V which is accelerated by a potential energy V due to the band gap between the first layer W and the second layer B. In other words, electrons that move from the first layer W to the second layer B are decelerated by potential energy V and return to the original kinetic energy E in the second layer B. As explained above, kinetic energy of electrons in the conduction band is modulated by potential energy due to the multi-layer structure.
When thicknesses of the first layer W and the second layer B are equal to order of quantum-wave wavelength, electrons tend to have characteristics of a wave. The wave length of the electron quantum-wave is calculated by Eqs. 1 and 2 using kinetic energy of the electron. Further, defining the respective wave number vector of first layer W and second layer B as K
W
and K
B
, reflectivity R of the wave is calculated by:
R
=(|
K
W
|−|K
B
|)/(|
K
W
|+|K
B
|)
=([
m
W
(
E+V
)]
½
−[m
B
E]
½
)/([
m
W
(
E+V
)]
½
+[m
B
E]
½
)
&e
Baumeister Bradley W.
Canare Electric Co., Ltd.
Eckert George
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