JPH0760892B2 - pnpn optical thyristor - Google Patents

Description

The present invention relates to a pnpn optical thyristor used as a semiconductor optical memory required for image processing, optical computers and the like.

[Conventional technology]

A semiconductor optical memory having an optical bistable function is a key device indispensable for future optical switching and parallel information processing systems. A pnpn optical thyristor having a structure as shown in FIG. 3 is known as a device having such a function. This pnpn optical thyristor is a journal of applied physics.
ed Physics), Volume 59, Pages 596-600,
It was reported in 1986 that an optical memory function can be realized by utilizing the non-linear current-voltage characteristic of a thyristor to generate light emission in the forward conduction state. p-type anode layer 17
Since the forbidden band width of the n-type cathode layer 11 is larger than the forbidden band width of the n-type base layer 33, carriers are confined in the n-type base layer 33 during forward conduction of the thyristor. Emits light. Therefore, by biasing to the non-conducting state and applying the trigger light to bring it into the conducting state, the light emitting state can be maintained even when the irradiation of the trigger light is stopped, and it can be used as an optical memory.

[Problems to be solved by the invention]

The light emitting area of such a conventional pnpn optical thyristor has a structure that is limited by mesa etching. However, due to application to parallel information processing of optical memory, miniaturization of the element size causes reliability problems. To do. Even if a passivation film made of polyimide or a dielectric material is attached to the side wall of the mesa for protection, long-term reliability cannot be expected.

An object of the present invention is to provide a pnpn optical thyristor which does not lose reliability even when miniaturized.

[Means for solving problems]

The pnpn optical thyristor of the present invention is provided on the surface of an n-type semiconductor substrate and has an n-type cathode layer having a predetermined forbidden band width and sequentially covering the n-type cathode layer. In a pnpn optical thyristor having a p-type base layer and an n-type base layer, and a p-type anode layer covering these base layers and having a wider forbidden band than these, the n-type base layer and the p-type base layer are sequentially arranged. Disordering by a p-type diffusion region including an n-type semiconductor layer and a multi-quantum well layer covering the multi-quantum well layer formed from the p-type anode layer to the n-type semiconductor layer and separated from the p-type base layer. That is, it is a light emitting region divided into regions.

[Action]

The multiple quantum well layer is disordered by impurity diffusion and ion implantation, and the band gap is also increased.

The carriers injected into the n-type base layer during conduction of the pnpn optical thyristor are efficiently relaxed in the non-disordered quantum well to generate light. Unlike the case of the mesa etching method, the light emitting portion is not exposed to the outside air during the manufacturing process, so that the reliability is improved. Crystal growth only needs to be done once. Light can be confined in the light emitting portion by using a material whose refractive index in the disordered region is lower than that of the multiple quantum well layer which is the light emitting portion.

〔Example〕

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

FIG. 1 is a sectional view of a semiconductor chip showing a main part of the first embodiment of the present invention.

In this embodiment, an n-type cathode layer 11 (Al _0.4 Ga _0.6 As layer) formed on the surface of an n-type semiconductor substrate 10 and having a predetermined band gap, and n
P-type base layer (Al _0.2 Ga _0.8 As layer) and n-type base layer, which are formed by sequentially coating the cathode cathode layer 11 and have a narrower forbidden band, and these base layers are coated to form a forbidden band. In a pnpn optical thyristor having a wide p-type anode layer 17 (Al _0.4 Ga _0.6 As layer), an n-type Al _0.2 Ga _0.8 As layer in which the aforementioned n-type base layer sequentially covers the p-type base layer 17 is formed.
13-1 and a multiple quantum well layer 16, including a multiple quantum well layer
Reference numeral 16 denotes a light emitting region which is formed from the p-type anode layer 17 to the n-type Al _0.2 Ga _0.8 As layer 13-1 and is partitioned by the disordered region by the p-type Zn diffusion region 19 which is separated from the p-type base layer 12. This disordered region is the overlapping portion of the multiple quantum well layer 16 and the Zn diffusion region 19.

Next, the manufacturing method of this embodiment will be described.

On the n-type semiconductor substrate 10 made of GaAs (impurity concentration N = 2 × 10 ¹⁸ km ^-3 ), Si-doped AlνGa _1- νAs (ν = 0.4, thickness d
= 2 μm, N = 2 × 10 ¹⁸ cm ⁻³ ) to form an n-type cathode layer 11 by epitaxial growth, and then Be-doped Al x Ga _1- x
As (x = 0.2, d = 5 nm, N = 1 × 10 ¹⁹ cm ⁻³ ) is epitaxially grown to form the p-type base layer 12.

Next, the n-type base layer is formed. This n-type base layer is n
Type Al _0.2 Ga _0.8 As layer 13-1, multiple quantum well layer 16, n-type Al _0.2 Ga
_It consists of _0.8 As layer 13-2. First, an n-type Al _0.2 Ga _0.8 As layer 13-1 having a thickness of 0.6 μm and an impurity concentration of 1 × 10 ¹⁷ cm ⁻³ is grown, and then an n-type GaAs layer 14 (d = 5 nm, N = 1 × 10 ^17). cm ^-3 )
And n-type Al wGa _1- wAs layer 15 (w = 0.2, d = 5 nm, N = 1 × 10 ¹⁷ cm
^-3 ) and 7 cycles are alternately laminated to form a multiple quantum well layer 16, and finally, an n-type Al _0.2 Ga _0.8 As layer 3-2 (d = 0.1 μm, N =
1 × 10 ¹⁷ cm ⁻³ ) is formed.

Next, AlxGa _1- xAs (x = 0.4, d = 0.5 μm, N = 2 × 10 ¹⁸ c
m ⁻³ ) to form a p-type anode layer 17 and then p −
Type GaAs (d = 0.4 μm, N = 2 × 10 ¹⁸ cm ^-3 ) was grown and p
-Type anode layer 17 is formed, and then p-type GaAs (d = 0.2 μm, N
= 2 × 10 ¹⁸ cm ^-3 ) and the anode contact layer 18
To form.

Next, Zn is selectively diffused deeper than the multiple quantum well layer 16 and Zn
A diffusion region 19 is formed. (The surface area of the multiple quantum well layer 16 which is not subjected to Zn diffusion treatment is a circle of 10 μmφ,
The light emission output is obtained in the direction of the arrow indicated by the broken line in the figure. ) Finally, the anode electrode 20 and the cathode electrode 21 are formed.

In the disordered region in which the quantum well structure has disappeared due to the diffusion treatment, the average composition of Al is X = 0.1. When viewed in the lateral direction (layer direction) from the n-type GaAs layer 14, a hetero barrier of AlGaAs corresponding to X = 0.1 exists at the Zn diffusion region 19. The forbidden band width of AlGaAs at X = 0.1 is about 125 meV larger than that of GaAs. In the forward conduction state after the thyristor conduction, the carriers are relaxed in the quantum well of the n-type GaAs layer 14 and are also confined in the lateral direction.

As the light emission output, an output of several 100 μW was obtained at 100 mA.

FIG. 2 is a perspective view of a semiconductor chip showing a main part of the second embodiment of the present invention.

In this embodiment, light is extracted in the end face direction. The layer structure is almost the same as that of the first embodiment. In this example, the mesa width is 12 μm and the length in the longitudinal direction is 100 μm.
After performing selective diffusion, mesa processing is performed. The width of the multiple quantum well layer 16 not subjected to the diffusion process is about 2 μm.

Note that the end faces of the Zn diffusion region 19 are hatched in parallel for convenience.

Although this embodiment has a mesa stripe structure, the light emitting region is partitioned by the Zn diffusion region 19 so that it is not easily affected by the mesa etching process.

〔The invention's effect〕

As described above, the present invention has the light emitting region in which the multiple quantum well layers are divided by the disordered region, and since the light emitting region is not exposed, it is not exposed to the outside air in the manufacturing process, The effect is that a highly reliable fine pnpn optical thyristor can be obtained.

Especially, this effect is remarkable in a pnpn optical thyristor or a semiconductor optical memory using a semiconductor material such as AlGaAs / GaAs which is easily oxidized.

[Brief description of drawings]

1 is a sectional view of a semiconductor chip showing a main part of a first embodiment of the present invention, FIG. 2 is a perspective view of a semiconductor chip showing a main part of a second embodiment of the present invention, and FIG. It is sectional drawing of the semiconductor chip which shows the principal part of a prior art example. 10 ... n-type semiconductor substrate, 11 ... n-type cathode layer, 12 ...
n-type base layer, 13-1, 13-2 ... n-type Al _0.2 Ga _0.8 As layer,
14 ... n-type GaAs layer, 15 ... n-type Al wGa _1- wAs layer, 16 ... multiple quantum well layer, 17 ... p-type cathode layer, 18 ... anode contact layer, 19 ... Zn diffusion region, 20 …… Anode electrode, 21 …… Cathode electrode, 22 …… Silicon oxide film, 31…
... p-type semiconductor substrate, 32 ... p-type buffer layer, 33 ... n-type base layer, 34 ... cathode contact layer.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01L 33/00 A

Claims (1)

[Claims] 1. An n-type cathode layer formed on the surface of an n-type semiconductor substrate and having a predetermined forbidden band width, and a p-type base layer having a narrower forbidden band formed by sequentially covering the n-type cathode layer. And a n-type base layer and a p-type anode layer that covers these base layers and has a wider band gap than these.
In the optical thyristor, the n-type base layer includes an n-type semiconductor layer and a multiple quantum well layer that sequentially cover the p-type base layer, and the multiple quantum well layer extends from the p-type anode layer to the n-type semiconductor layer. A pnpn optical thyristor, which is a light emitting region defined by a disordered region formed by a p-type diffusion region separated from the p-type base layer.