JP2527197B2 - Optical integrated device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical integrated device, and in particular, so-called crosstalk caused by light, in which leakage of light from a light emitting device portion affects the operation of an electronic element portion. The structure for preventing

[Conventional technology]

Conventionally, light emitting devices such as LDs (laser diodes) and LEDs (light emitting diodes) and electronic devices such as transistors have been configured as individual components in the circuit, but in recent years, due to an increase in the modulation frequency, the inductance of the wiring has increased due to the performance. Since it is no longer possible to ignore the effect of the above, it is necessary to reduce the stray capacitance to improve the high-speed response, and to further reduce the size and cost, these are integrated on the same semiconductor substrate. The development of the structure formed by the conversion has been actively carried out.

Figure 1 shows the LD and HBT among such optical integrated devices.
It is sectional drawing which shows one Example which integrated (hetero bipolar transistor). In the figure, (1) is a semi-insulating InP substrate (hereinafter referred to as substrate), and (2) is an n ⁺ type I-type substrate.
Conductive layer made of nP single crystal (Sn-doped, carrier concentration 5 ×
10 ¹⁸ cm ^-3 , thickness 1 μm), (3) laser diode section (hereinafter referred to as LD section), (4) n-type InP buffer layer (Te-doped, carrier concentration 1 × 10 ¹⁸ cm ^-3) , Thickness 2μ
m) and (5) are p-type InP current block layers (Zn-doped,
Carrier concentration 2 × 10 ¹⁸ cm ^-3 , thickness 1.5 μm, (6) is n-type InP current block layer (Te-doped, carrier concentration 3)
× 10 ¹⁸ cm ^-3 , thickness 0.5 μm), each semiconductor layer (2),
(4) to (6) are, for example, MOCVD (metal chemical growth), MBE (molecular beam epitaxy) or LPE.
It is formed by any one of the methods (liquid phase epitaxial growth method). (7) is a stripe-shaped groove,
The respective phases (4) to (6) described above are formed by etching with hydrochloric acid using the Lingrafi technique. (8) is n-type In
P lower cladding layer (Te-doped, carrier concentration 1 × 10 ¹⁸ c
m ^-3 ), (9) are InGaAsP active layers (undoped, thickness 0.15
μm) and (10) are p-type cladding layers on InP (Zn-doped,
Carrier concentration 7 × 10 ¹⁷ cm ^-3 , thickness 3 μm), (11) is p
Type InGaAs (P), LD contact layer (Zn-doped, carrier concentration 1 × 10 ¹⁸ cm ^-3 , thickness 0.6 μm), and each of these layers (8) to (11) is MOCVD, MBE or LPE. The formation of the LD part (3) is completed by sequentially forming the LD part (3). At this stage, each layer (4) to (6), (10),
(11) is formed over the entire surface of the n ⁺ type InP conductive layer (2). (12) is a hetero bipolar transistor section (hereinafter referred to as HBT section), (13) is an n-type InP collector layer (Sn-doped, carrier concentration 1 × 10 ¹⁷ cm ^-3 , thickness 2.5 μ)
m) and (14) are p-type InGaAsP base layers (Zn-doped, carrier concentration 1 × 10 ¹⁷ cm ^-3 , thickness 0.24) are p-type InGaAsP
Base layer (Zn-doped, carrier concentration 1 × 10 ¹⁷ cm μm),
(15) is n-type InP emitter layer (Sn-doped, carrier concentration 5 × 10 ¹⁷ cm ^-3 , thickness 0.7 μm), (16) is n-type InGaA
sP HBT contact layer (Sn-doped, carrier concentration 1 × 10 ¹⁸
In order to form each of these layers (13) to (16) with a cm ^-3 thickness of 1 μm), first, the LD contact layer (11) of the LD section (3) is formed.
For example, a SiO ₂ film (not shown) is formed on the above, and each layer (4) at a portion where the HBT part (12) is formed is formed by using the film as a mask.
~ After removing (6), (10), (11) by etching with hydrochloric acid, etc., each layer (13) ~ (16) is selectively grown by MOCVD, MBE or LPE. Let Then, for example, Mg is injected to form the p ⁺ -type diffusion region (17) in a ring shape, and the formation of the HBT portion (12) is completed.

(18) is an isolation groove, and (19) is an element isolation layer made of, for example, polyimide of an insulating machine. First, the LD section (3) and the HBT section (1
During 2), etch each formed layer with hydrochloric acid etc.
^The depth reaches the interface with the ⁺ type InP conductive layer (2) and the width is 3 to
A separation groove (18) of 4 μm is provided, and then in the groove (18),
A device isolation layer (19) is formed by embedding polyimide.

(20) is an insulating film made of, for example, SiO ₂ , and is formed to a thickness of about 1000 Å by, for example, the CVD method.

(21) is a P-side laser electrode, and (22) is a base electrode, which is formed in an annular shape. (23) is an emitter electrode,
The elements are completed by connecting each other by wiring (not shown) and cleaving the LD end face.

In the above optical integrated device, the collector layer (13) of the HBT section (12) and the buffer layer (4) corresponding to the cathode (n-side laser electrode) of the LD section (3) are low resistance conductive layers ( They are connected in series in 2).

When the emitter electrode (23) is grounded and the P-side laser electrode (anode) (21) is positively biased, the base (22)
-When the voltage between the emitter (23) electrodes is zero, the LD section (3)
Since a current flows through it and the state is in a normally-on state as it is, the base electrode (22) is negatively biased or the emitter electrode (23) is level-shifted if necessary.

Base (22) in this state - when modulates between emitter (23) electrodes, (the beta current amplification factor of the HBT, I _B is the base current) beta · I _B during which flows a collector current of.

In HBT, holes are effectively confined in the base layer (14), so a high β value can be obtained, and a large laser or
In a normal HBT, the forbidden band width of the emitter layer and collector layer is
It has a size larger than the forbidden band width of the base layer.

Now, when the forward bias voltage of the pn junction to LD from HBT is applied, the active layer of the collector current beta · I _B from upper Kuratsudo layer (10) as the drive current of the LD of the stripe-shaped groove (7) ( 9) Concentrated flow to the upper and lower cladding layers (10),
Holes and electrons are injected from (8). However, these injected carriers are trapped in the active layer (9) by the barrier at the heterojunction interface and recombine to emit modulated light.

Further, the absorption of light by the current block layers (5) and (6) causes a difference in the refractive index in the horizontal direction in the active layer (3), which limits the spread of light in the lateral direction and stabilizes the lateral mode. The light guided in this manner is emitted by a laser using a Fabry-Perot resonator composed of opposing cleavage end faces that are perpendicular to the depth direction of the stripe-shaped groove (7). Leads to oscillation.

In the above optical integrated device, the device isolation layer (19)
By providing the LD, the LD and HBT can perform their unique functions without interfering with each other.

[Problems to be solved by the invention]

In the above optical integrated device, LD and HBT are compactly integrated and formed on the same substrate.
New problems are occurring.

That is, since LD and HBT are very close to each other, light leakage from LD may cause so-called cross talk (hereinafter, simply referred to as crosstalk) caused by light, which affects the operation of HBT. Is. In particular, HBT is
Since the structure is the same as that of the transistor, an amplifying effect is exhibited with respect to leaked light, and the influence of crosstalk is further increased.

The present invention has been made to solve the above problems, and an object thereof is to obtain an optical integrated device in which crosstalk does not occur.

[Means for Solving the Invention]

An optical integrated device according to the present invention has at least a light emitting device section and a heteropolar transistor section formed on a substrate, and an emitter layer, a base layer, a collector to which an electric field is applied during operation in the configuration of the heterobipolar transistor section. The forbidden band width of the layer is formed larger than that of the active layer of the light emitting element section.

[Action]

In the present invention, the forbidden band width of the emitter layer, the base layer, and the collector layer of the hetero-bipolar transistor section is formed larger than that of the active layer of the light emitting element section, so that the light leaked from the active layer is Even if it reaches the emitter layer, the base layer, and the collector layer, it is not absorbed, and therefore crosstalk does not occur.

〔Example〕

The configuration of an embodiment of the present invention is similar to that of the conventional one shown in FIG. However, the active layer (9) should be In0.65Ga0.35
As0.79P0.21 with p-type In0.76Ga0.24A for the base layer (14)
s0.55P0.45 respectively, and the forbidden band of the base layer (14) is made larger than that of the active layer (9). Also, the emitter layer (15) above and below the base layer (14) is formed. ),
The collector layer (13) also has a band gap larger than that of the active layer (9).

In the optical integrated device configured as described above, the light leaked from the active layer (9) is not absorbed even if it reaches the emitter layer (15), the base layer (14) and the collector layer (13). The behavior of is not affected.

In addition, in the said Example, each layer (2), (4)-.
The conductivity types of (6), (8), (10), (11), and (13) to (17) may be opposite to each other. Also, although the LD part (3) and the HBT part (12) are each shown to be formed by one, it is possible to form a plurality with other electronic elements having functions such as modulation, amplification and switching. It goes without saying that you can pay attention.

Furthermore, although an example of a combination of LD and HBT is shown, a combination of LED and HBT may be used.

〔The invention's effect〕

As described above, according to the present invention, the forbidden band width of the emitter layer, the base layer, and the collector layer of the hetero-bipolar transistor section is formed larger than that of the active layer of the light emitting element section. Is not absorbed even when it reaches the base layer, so that there is an effect that an optical integrated device in which crosstalk does not occur can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a conventional one. In the figure, (1) is a semi-insulating InP substrate (substrate),
(3) is laser diode part (LD part), (9) is InGaAs
P active layer, (12) is the hetero bipolar transistor section (H
(BT portion) and (14) are p-type InGaAsP base layers. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. In an optical integrated device in which at least a light emitting device portion and a hetero bipolar transistor portion are integrated on a substrate, the forbidden band widths of the emitter layer, base layer and collector layer of the hetero bipolar transistor portion are the light emitting element. An integrated device characterized in that it is formed to be larger than that of the active layer in some parts.