Active solid-state devices (e.g. – transistors – solid-state diode – Bipolar transistor structure – With base region having specified doping concentration...
Reexamination Certificate
1999-10-22
2002-01-08
Lee, Eddie (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Bipolar transistor structure
With base region having specified doping concentration...
C257S015000, C257S017000, C257S020000, C257S024000, C257S187000, C257S192000, C257S197000
Reexamination Certificate
active
06337508
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a transistor having a new junction structure with whose dynamic resistance is lowered.
2. Description of the Related Art
Bipolar transistors which has a pnp or an npn junction structure have been known. Electric current, which flows when the forward voltage is applied to the transistor having a pn junction structure, increases rapidly at the point where the forward voltage exceeds the potential difference between the conduction bands of p and n layers. The larger gradient of the characteristic carve between electric current and voltage in the dynamic range is, the more suitable the transistor becomes to use as various devices.
However, a problem persists in the gradient. The gradient of electric current and voltage characteristics could not be varied because it is determined by materials which form the transistor. Therefore, further improvement has been required, as presently appreciated by the present inventors.
As a countermeasure, reflecting carriers by forming cladding layers with a multi-quantum well structure of a first and a second layers as a unit in a laser diode (LD) has been suggested by Takagi et al. (Japanese Journal of Applied Physics. Vol.29, No.11, November 1990, pp.L1977-L1980). Although it can be led that a band gap energy is used as an alternative of a kinetic energy, this reference does not teach or suggest values of kinetic energy of carriers to be considered and the degree of luminous intensity improvement is inadequate.
SUMMARY OF THE INVENTION
The inventor of the present invention conducted a series of experiments and found that the suggested thicknesses of the first and the second layers by Takagi et al. were too small to reflect carriers, and that preferable thicknesses of the first and second layers are 4 to 6 times larger than those suggested by Takagi et al. Further, the present inventors thought that multiple reflection of quantum-waves of carriers might occur by a multi-layer structure with different band width, like multiple reflection of light by a dielectic multi-film structure. And the inventors thought that it would be possible to vary the I-V characteristic of carriers when the external voltage is applied to the device by the quantum-wave reflection. As a result, the inventors invented a preferable quantum-wave interference layer and applications of the same.
It is, therefore, an object of the present invention to provide a transistor having a junction structure with considerably lower dynamic resistance by forming a quantum-wave interference layer.
In light of these objects a first aspect of the present invention is a transistor constituted by forming a quantum-wave interference layer having plural periods of a pair of a first layer and a second layer in a base region or a channel region, the second layer having a wider band gap than the first layer. Each thickness of the first and the second layers is determined by multiplying by an odd number one fourth of quantum-wave wavelength of injected minority carriers in each of the first and the second layers.
The second aspect of the present invention is a transistor constituted by a quantum-wave interference layer having plural periods of a pair of a first layer and a second layer in a base region or a channel region. The second layer has a wider band gap than the first layer. A &dgr; layer is included for sharply varying energy band and is formed between the first and the second layers. Each thickness of the first and the second layers is determined by multiplying by odd number one fourth of quantum-wave wavelength of injected minority carriers in each of the first and the second layers, and a thickness of the &dgr; layer is substantially thinner than that of the first and the second layers.
The third aspect of the present invention is a transistor having injected carriers existing around the lowest energy level of the second layer.
The fourth 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 a Plank's constant, effective mass of minority carriers injected into the first layer, effective mass of minority carriers in the second layer, kinetic energy of minority carriers injected into the second layer, potential energy of the second layer to the first layer, and odd numbers, respectively. An minority carriers injected into the second layer are preferably existing around the lowest energy level of the second layer.
The fifth aspect of the present invention is a transistor having a plurality of partial quantum-wave interference layers I
k
in a base region or a channel region with arbitrary periods T
k
including a first layer having a thickness of D
Wk
and a second layer having a thickness of D
Bk
and arranged in series. The thicknesses of the first and the second layers satisfy the formulas:
D
Wk
=n
Wk
&lgr;
Wk
/4
h
/4
=n
Wk[2
m
Wk
(
E
k
+V
)]
½
(3)
and
D
Bk
=n
Bk
&lgr;
Bk
/4
=n
Bk
h
/4(2
m
Bk
E
k
)
½
(4)
In Eqs. 3 and 4, E
k
, m
Wk
, m
Bk
, and n
Wk
and n
Bk
represent plural kinetic energy levels of minority carriers injected into the second layer, effective mass of minority carriers with kinetic energy E
k
+V in the first layer, effective mass of minority carriers with kinetic energy E
k
in the second layer, and arbitrary odd numbers, respectively.
The plurality of the partial quantum-wave interference layers I
k
are arranged in series from I
1
, to I
j
, where j is a maximum number of k required to form a quantum-wave interference layer as a whole.
The sixth aspect of the present invention is a transistor having a quantum-wave interference layer with a plurality of partial quantum-wave interference layers arranged in series with arbitrary periods. Each of the plurality of partial quantum-wave interference layers is constructed with serial pairs of the first and second layers. The widths of the first and second layers of the serial pairs are represented by (D
W1
, D
B1
), . . . (D
Wk
, D
Bk
), (D
Wj
, D
Bj
). (D
Wk
, D
Bk
) is a pair of widths of the first and second layers and is defined as Eqs. 3 and 4, respectively.
The seventh aspect of the present invention is to form a &dgr; layer between a first layer and a second layer which sharply varies the energy band and has a thickness substantially thinner than that of the first and the second layers.
The eighth aspect of the present invention is to constitute a quantum-wave incident facet in the quantum-wave interference layer by a second layer with enough thickness for preventing conduction of minority carriers injected into the first layer by a tunneling effect.
The ninth aspect of the present invention is a bipolar transistor having the quantum-wave interference layer in a base region.
The tenth aspect of the present invention is a field effect transistor having the quantum-wave interference layer in a channel region.
FIRST, THIRD AND FOURTH ASPECTS OF THE PRESENT INVENTION
The principle of the quantum-wave interference layer in a pn junction structure of, for example, npn-transistor according to the present invention is explained hereinafter.
FIG. 1
shows a conduction band of a multi-layer structure, formed in a p-layer, i.e., in a base or channel area, with plural periods of a pair of a first layer W and a second layer B. A band gap of the second layer B is wider than that of the first layer W. Electrons, or minority carriers, which have been injected into the p-layer, conduct from left to right as shown by an arrow in FIG.
1
. Among the electrons, those that existing around the bottom of the second layer B are likely to contribute to conduction. The electrons around the bottom of the second layer B has a kinetic energy E. Accordingly, the electrons in the f
Baumeister Bradley W.
Canare Electric Co., Ltd.
Lee Eddie
LandOfFree
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