JP2876642B2 - Quantum well laser - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor laser.

[Conventional technology]

In a conventional quantum well laser having a quantum well structure as an active region, the energy level of carriers in the quantum well is higher than the potential of the quantum well layer, and the wave function is sinusoidal. This quantum confinement has an excellent feature that the oscillation threshold current is extremely small (Applied Physics Letters [Applide Phys
ics Letters], Vol. 51, pp. 2094, 1987).

[Problems to be solved by the invention]

However, in the above-described conventional quantum well laser, the wave function of the carrier is sinusoidal, and the distribution of the carriers is locally concentrated.
It is difficult to reduce the oscillation threshold current more than this,
There is also a disadvantage that the length of the resonator cannot be shortened.

[Means for solving the problem]

Means provided by the present invention in order to solve the above-described problems is a semiconductor laser having a quantum well structure including a quantum plane, a quantum wire, or a quantum box as an active region, and a deep potential material formed in the quantum well structure. A deep potential region, and a shallow potential region made of a shallow potential material sandwiched between the deep potential regions, wherein the energy level of carriers in the quantum well structure is close to the potential of the shallow potential region and the wave function is rectangular. It is configured to be close to.

The energy levels and wave functions of electrons and holes can be obtained by solving the Schrodinger equation. Assuming that the potential having the band structure is V (x), the Schrodinger equation is Becomes Where u is the wave function, E is the energy level,
x is coordinates, m is effective mass, Is a constant obtained by dividing the Planck constant by 2π.

By adjusting the thickness of each of the quantum barrier layer, the deep potential region, and the shallow potential region, the energy levels of electrons and holes can be made substantially equal to the potential of the shallow potential region. In that case, the spatial change of the wave function in the shallow potential region is small, and the whole has a shape close to a rectangle.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of one embodiment of the present invention. n-type GaAs
An n-type clad layer (thickness 1 μm) 11 of n-type Al _0.7 Ga _0.3 As and a light guide layer (thickness 1000 °) of n-type Al _0.2 Ga _0.8 As are formed on a substrate 10 of In _0.2 Ga _0.8 As. Deep potential region (thickness 10 mm) 13, shallow potential region (thickness 100 mm) 14 made of GaAs, deep potential region (thickness 10 mm) 15 made of In _0.2 Ga _0.8 As, p-type Al _0.2 Ga _0.8 As Light guide layer (thickness 1000 mm) 16, p-type Al _0.7 Ga _0.3 As
A p-type cladding layer (thickness: 1 μm) 17 and a cap layer (thickness: 3000 °) 18 made of p-type GaAs are crystal-grown by molecular beam epitaxy, and then p-electrodes 19 and n are deposited by vapor deposition.
The electrode 20 was formed.

FIG. 2 is a diagram schematically showing the band structures of the quantum well regions 13, 14, and 15, and the wave functions of carriers. The upper side is the conduction band potential 21 and the electron wave function 22, and the lower side is the valence band potential 23 and the hole wave function 24. In this structure, the wave function 2 in the deep potential regions 13 and 15
2, 24 change with a large curvature, and in the shallow potential region 14, change with a small curvature. Since the energy level of the carriers is close to the value of the potential in the shallow potential region 14, the wave functions 22 and 24 have a substantially constant value in the shallow potential region 14, and the entire wave functions 22 and 24 have a shape close to a rectangle.

Since the wave functions 22 and 24 have a rectangular shape, a space capable of interacting with light is increased, so that the light confinement ratio of the semiconductor laser can be increased.

The oscillation threshold current density of this semiconductor laser was very low at 150 A / cm ^2, and good laser oscillation was obtained even if the cavity length was shortened to 100 μm.

Although the quantum plane is used as the active region in the above-described embodiment, the present invention is not limited to this, and a quantum wire or a quantum box may be used.

Although a GaAs-based semiconductor material is used in the above-described embodiment, the present invention is not limited to this, and another semiconductor material may be used.

〔The invention's effect〕

As described above, according to the present invention, a semiconductor laser having a high light confinement ratio and a small oscillation threshold current can be obtained.

In the embodiment, the description of the mode control structure, the current confinement structure and the like is omitted, but the structure for the mode control and the current confinement may be any structure such as a conventionally used stripe structure.

[Brief description of the drawings]

FIG. 1 is a sectional view of a quantum well laser according to one embodiment of the present invention, and FIG. 2 is a schematic view of a quantum well structure. 10 ... substrate, 11 ... n-type cladding layer, 12 ... light guide layer, 13 ... deep potential region, 14 ... shallow potential region, 15 ... deep potential region, 16 ... light guide layer,
17 p-type cladding layer, 18 cap layer, 19 p-electrode, 20 n-electrode, 21 potential of conduction band, 22
… Electron wave function, 23 …… valence band potential, 24
...... Hole wave function.

Claims (1)

(57) [Claims] 1. A semiconductor laser having a quantum well structure comprising a quantum plane, a quantum wire, or a quantum box as an active region, wherein the active region has a deep potential quantum well layer made of a deep potential material; And a shallow potential quantum well layer made of a shallow potential material sandwiched therebetween, wherein the energy level of carriers in the active region is close to the potential of the shallow potential quantum well layer and the wave function is close to rectangular. Well laser.