JPH0371797B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to improvements in quantum well semiconductor lasers.

[Conventional technology]

In a quantum well type semiconductor laser, a quantum well layer that acts as an active layer is sandwiched between carrier confinement layers, and carriers are injected into the quantum well layer through the carrier confinement layer. It is common to have a configuration in which light is generated, the light is amplified, and based on this, laser oscillation is obtained. Such a quantum well type semiconductor laser has features such as being able to operate with a lower threshold current and being able to easily control the laser oscillation wavelength compared to other types of semiconductor lasers. However, in conventional quantum well type semiconductor lasers, in the process of carriers passing through the carrier confinement layer and entering the quantum well layer, due to the difference in energy band gap between the quantum well layer and the carrier confinement layer, quantum It has been common practice to have a structure in which phonons are forced to be emitted in the region of the well layer where light is generated or where the light is amplified. Therefore, in the case of a conventional quantum well semiconductor laser, in addition to light having a wavelength corresponding to the energy between electronic levels, the above-mentioned phonons and carriers are
Interaction with light generates light with a wavelength corresponding to the energy of the phonon-mediated transition, making it difficult to stably obtain laser oscillation with a clean spectrum and not exhibiting good current-light output characteristics. It had drawbacks such as. Furthermore, conventional quantum well type semiconductor lasers typically have a configuration that makes it impossible to uniformly inject and accumulate carriers in each part of the quantum well layer. For this reason, conventional quantum well type semiconductor lasers have disadvantages such as poor laser oscillation efficiency and high threshold current value for laser oscillation. Therefore, the present invention aims to propose a novel quantum well type semiconductor laser that does not have the above-mentioned drawbacks.

【Example】

The figure shows an embodiment of a quantum well type semiconductor laser according to the present invention, in which a plurality of M quantum well layers A ₁ to A _M in which two quantum well layer parts a1 and a2 are arranged in parallel with each other, A plurality (M+
1) carrier confinement layers B ₁ to _{B M+1} . In this case, the quantum well layers A ₁ to A _M have a smaller energy band gap than the carrier confinement layers B ₁ to _{B M+1} , and are made of, for example, GaAs. Further, the carrier confinement layers B ₁ to _{B M+1} are made of Al _1-X Ga _X As (0<X<1). Further, the quantum well layers A ₁ to A _M have a thickness on the order of 100 Å, for example. Furthermore, quantum well layer portion a of quantum well layers A ₁ to A _M
1, and the carrier confinement layer portions b1 of the carrier confinement layers B ₁ to _{B M+1} have a p ⁺ type. Further, the quantum well layer portions a2 of the quantum well layers A ₁ to A _M have n-type, and the carrier confinement layer portions b2 of the carrier confinement layers B ₁ to _{B M+1} have the quantum well layers A ₁ to A Since it has a higher impurity concentration than the quantum well layer a2 of _M , it has n ⁺ type. The quantum well layers A ₁ to A _M and the carrier confinement layers B ₁ to _{B M+1} described above are the carrier confinement layers B _i and
B _i+1 (where i=1, 2, ......M) are respectively arranged on the opposing main surfaces of the quantum well layer A _i , and the carrier confinement layers B _i and B _i+1 are carrier confinement layer part b1 to quantum well layer part a1 of quantum well layer A,
The carrier confinement layers B _i and the carrier confinement layer b2 of B _i+1 are laminated in a state in which they are connected to the quantum well layer portion a2 of the quantum well layer A _i . In practice, such a configuration requires a carrier confinement layer.
A plurality of ( _M+1 ) first semiconductor layers serving as the carrier confinement layer portion b2 of B ₁ to B M+1 and a quantum well layer A ₁
A plurality of M second quantum well layer portions a2 of ~A _M
and semiconductor layers are alternately stacked one after another by, for example, molecular beam epitaxial crystal growth,
Next, it can be manufactured by selectively diffusing p-type impurities, such as sulfur or tin, into the laminate from one side in the stacking direction. Further, the electrode E1 is ohmicly connected to the carrier confinement layer portion b2 of the carrier confinement layer _B1 ,
Further, an electrode E2 is ohmicly connected to the carrier confinement layer portion b1 of the carrier confinement layer B _M+1 . The above is the configuration of the embodiment of the quantum well type semiconductor laser according to the present invention. According to the quantum well type semiconductor laser according to the present invention having such a configuration, if a DC power source is connected between the electrodes E1 and E2 with the polarity of the electrode E2 being positive, electrons can be transferred from the electrode E1 to a carrier closed state. Passing through the carrier confinement layer part b2 of the confinement layer B _i ,
It enters the quantum well layer part a2 of the quantum well layer _{A i ,} and then passes through the junction (pn junction in this case) J _i between the quantum well layer parts a1 and a2 of the quantum well layer A i.
It enters the quantum well layer a1 of A _i . Therefore, electrons enter the quantum well layer portion a1 of the quantum well layers A ₁ to A _M. On the other hand, holes are transferred from the electrode E2 to the carrier confinement layer.
It passes through the carrier confinement layer b1 of B _i+1 and enters the quantum well layer a1 of the quantum well layer A _i . Therefore, holes enter quantum well layer portion a1 of quantum well layers A ₁ to A _M. Therefore, electrons and holes are recombined within the quantum well layer portion a1 of the quantum well layer _Ai , and light is generated and the light is amplified. Note that in this case, the generation of light and the amplification of the light mainly occur in a region near the junction J _i in the quantum well layer portion a1 of the quantum well layer A _i . Therefore, laser oscillation can be obtained by making at least the opposing end surfaces (planes parallel to the plane of the paper) of the quantum well layers A ₁ to A _M as Fabry-Perot reflecting surfaces, and the laser oscillation light , quantum well layer
The light can be emitted to the outside from one of the opposing end faces of A _i . Therefore, the quantum well type semiconductor laser according to the present invention described above can function as a semiconductor laser. By the way, in the quantum well type semiconductor laser according to the present invention, as described above, electrons enter the carrier confinement layer portion b2 of the carrier confinement layers B ₁ to _{B M+1.}
, enters the quantum well layer portion a2 of the quantum well layers A ₁ to A _M , respectively, and then enters the quantum well layer portion a1 of the quantum well layers A ₁ to A _M , and the function as the semiconductor laser described above is achieved. However, since there is a difference in energy band gap between the carrier confinement layer part b2 and the quantum well layer part a2, the electrons are transferred to the carrier confinement layer part b2 of the carrier confinement layers B ₁ to _{B M+1.} from,
Quantum well layer portions a2 of quantum well layers A ₁ to A _M , respectively.
In the process of entering the quantum well layer a2, phonons are emitted. However, electrons are bonded from quantum well layer portion a2 of quantum well layers A ₁ to _{A M} to quantum well layer portion a1.
In the process of entering through J ₁ to J _M , the quantum well layer part a1
Since there is no difference in energy band gap between and a2, phonon emission is not substantially accompanied. Therefore, in the region near the junctions J ₁ to J _M of the quantum well layer portions a1 of the quantum well layers A ₁ to A _M , which generate light or amplify the light, phonon emission is substantially not accompanied. do not have. Therefore, according to the quantum well semiconductor laser according to the present invention, it is substantially possible to generate light having a wavelength corresponding to the energy of the phonon-mediated transition through the interaction of phonons, carriers, and light. Instead, substantially only light having a wavelength corresponding to the energy between the electronic levels is generated. Therefore, according to the above-described quantum well type semiconductor laser according to the present invention, laser oscillation light can be stably obtained with a clean spectrum, and exhibits good current-light output characteristics. In addition, there are a plurality of M quantum well layers A ₁ to _{A M} ,
In addition, carrier confinement layers B ₁ to _{B M+1} and multiple (M
+1) The quantum well layer portions a1 of the quantum well layers A ₁ to A _M and the carrier confinement layer portions b1 of the carrier confinement layers B ₁ to _{B M+1} are laminated in alternating order. connected to the electrode E2, and also has a quantum well layer A ₁
~A _M quantum well layer a2 and carrier confinement layer B ₁
〜B _M+1 carrier confinement layer portion b2 are similarly stacked alternately and connected to the electrode E1, and in this case, the carrier confinement layer portion _b2 of 〜B _M+1 Since the part b2 has a higher n-type impurity concentration than the quantum well layer part b2 of the quantum well layers A ₁ to A _M , the carrier confinement layer part b2 of the carrier confinement layer B _i and the quantum well of the quantum well layer A _i The carrier confinement layer part b2 of the carrier confinement layers B ₁ to _{B M+1} has the same barrier height with the well layer part a2 as the quantum well layer part a2 of the quantum well layers A ₁ to A _M The impurity concentration is lower than that when the impurity concentration is present, and therefore, the quantum well layer portions a2 of the quantum well layers A ₁ to A _M have substantially equal amounts of electrons, and the carrier confinement layers B ₁ to _{B M+1} A larger amount of carrier confinement layer b2 is implanted than in the case where the n-type impurity concentration is the same as that of quantum well layer a2 of quantum well layers A _{1 to} A _M. The built-in voltage between the confinement layer parts b1 and b2 and the built-in voltage between the quantum well layer parts a1 and a2 of the quantum well layer A _i (compared to the built-in voltage between the carrier confinement layer parts b1 and b2 of the carrier confinement layer B _i carrier confinement layer B ₁ ~
The carrier confinement layer part b2 of B _M+1 is the quantum well layer A ₁
It is larger than the case where the n-type impurity concentration is the same as the quantum well layer portion a2 of ~A _M , and therefore, the carrier confinement layer portion b2 of the carrier confinement layer B _i is transferred from the carrier confinement layer portion b1 of the carrier confinement layer B i by this amount. The amount of electron leakage is when the carrier confinement layer portion b2 of the carrier confinement layers B ₁ to _{B M+1} has the same n-type impurity concentration as the quantum well layer portion a2 of the quantum well layers A ₁ to _{A M} Comparatively small. Therefore, according to the quantum well semiconductor laser according to the present invention, the above-described laser oscillation can be achieved with higher oscillation efficiency than the conventional quantum well semiconductor laser, and the threshold current value of the laser oscillation can be In the conventional quantum well semiconductor laser, the carrier confinement layer portion b2 of the carrier confinement layers B ₁ to B _M+1 has the same n-type impurity concentration as the quantum well layer portion a2 of the quantum well layers A ₁ to _{A M} It has great features such as being able to lower the cost compared to other cases. Note that the above description merely shows an example of the present invention, and the electrodes E1 and E2 are connected to the carrier confinement layer portion b2 of the carrier confinement layer _B1 and the carrier confinement layer B _M through the electrode attachment layer, respectively. ₊₁ carrier confinement layer section b1, and furthermore, the electrodes E1 and E2 can be connected to the carrier confinement layer section _b1 of carrier confinement layer B1, respectively.
The carrier confinement layer B _M+1 may be connected to the carrier confinement layer part b2 of the carrier confinement layer B M+1, and various other modifications and changes may be made without departing from the spirit of the present invention. .

[Brief explanation of drawings]

The figure is a schematic cross-sectional view showing an embodiment of a quantum well type semiconductor laser according to the present invention. A ₁ to _{A M} ... quantum well layer, a1, a2... quantum well layer A ₁ to quantum well layer part of A _M , B ₁ to _{B M+1} ... carrier confinement layer, b1, b2... carrier Carrier confinement layer portion of confinement layer B ₁ to B _M+1 , J ₁ to J _M ……
Junction.

Claims (1)

[Scope of Claims] 1. A plurality of M quantum well layers A ₁ , A ₂ , in which the first and second quantum well layer portions are arranged in parallel with each other.
... A _M , and a plurality of (M+1) carrier confinement layers B ₁ , B ₂ , ... B _{M+1 in} which the first and second carrier confinement layer portions are arranged in parallel with each other. a first quantum well layer portion of the quantum well layers A ₁ to A _M and a first quantum well layer portion of the carrier confinement layers B ₁ to _{B M+1} ;
The carrier confinement layer portion of has p type, the second quantum well layer portion of the quantum well layers A ₁ to A _M has n type, and the carrier confinement layer portion B ₁ to B _M has n type. The second carrier confinement layer portion of ₊₁ has an n ⁺ type by having a higher impurity concentration than the second quantum well layer portions of the quantum well layers A ₁ to A _M , and The quantum well layers A ₁ to A _M and the carrier confinement layers B ₁ to B _M+1 have the carrier confinement layers B _i and B _i+1 (where i=1, 2,...M). , respectively arranged on the opposing first and second main surfaces of the quantum well layer A _i , and the carrier confinement layers B _i and
The first carrier confinement layer part of B _i+1 is placed in the first quantum well layer part of the quantum well layer A _i , and the second carrier confinement layer part of the carrier confinement layers B _i and B _i+1 is The first carrier confinement layer part is stacked in such a manner that the layer part is connected to the second quantum well layer part of the quantum well layer A _i , and the first carrier confinement layer part is connected to the second carrier confinement layer part of the carrier confinement layer _B1 . An electrode is connected to the first carrier confinement layer portion of the carrier confinement layer B _M+1 ;
A quantum well semiconductor laser characterized in that a second electrode is connected.