Patent Description:
A VCSEL with monolithically integrated photodiode, commonly denoted as ViP, may be used in sensors for the measurement of e.g. distances, displacements or velocities. All these measurements may be based on the principle of self-mixing interference (SMI). Another application of VCSELs is the measurement of particle densities, which enables for example a measurement of air quality. Devices of this type might be simple enough to be even integrated in mobile phones.

Typically, ViPs are based entirely on the AlGaAs material system. A VCSEL device of this type is disclosed in <CIT>. The quantum well(s) of the active region of the optical resonator as well as the layer stack of the photodiode comprise AlGaAs and GaAs material.

<CIT> discloses a VCSEL with an intracavity quantum well photodiode. This known VCSEL device uses a quantum well photodiode layer stack and a quantum well layer stack in the active region of the optical resonator, both made of InGasAs material. A similar VCSEL is disclosed in <CIT>, which discloses the preamble of claim <NUM>. <CIT> discloses a VCSEL with an photodetector having a thin absorption layer of InGaAs with an indium content of a few percent.

VCSELs based on the AlGaAs material system provide laser emission at a wavelength of about <NUM>. VCSELs using AlGaAs for the active region of the laser and GaAs for the photodiode do not allow for much longer emission wavelengths.

It may be desirable to provide ViPs which are able to emit laser light in a wavelength range above <NUM> which is far less visible to the human eye so that essentially invisible sensors based on ViPs are available.

It is an object of the present invention to provide an improved Vertical Cavity Surface Emitting Laser device with monolithically integrated photodiode which enables laser light emission in a wavelength range above <NUM>, e.g. in a wavelength from <NUM> to <NUM>.

It is a further object to provide an optical sensor with improved light detection characteristics and thus enabling more exact measurements with the sensor.

It is a further object to provide a method of producing a VCSEL with monolithically integrated photodiode.

According to the invention, a Vertical Cavity Surface Emitting Laser (VCSEL) device according to claim <NUM> is provided.

Using InGaAs or GaAs (x=<NUM>) as the material system for the active region of the optical resonator enables a VCSEL device which may provide laser light emission in a wavelength range above <NUM>. Using InGaAs as the material system for the light absorption region of the photodiode enables light detection in the for-mentioned wavelength range. By mixing indium arsenide (InAs) and gallium arsenide (GaAs), the band gap of the resulting indium gallium arsenide (InGaAs) can be set. The band gap depends on the ratio of indium content to gallium content in the compound semiconductor. The more indium content in comparison to gallium content in the compound semiconductor material, the lower is the band gap and, thus, the longer is the wavelength emitted by the VCSEL.

At first glance it appears to be straightforward to replace the GaAs-photodiode of the conventional VCSELs by a similar one based on InGaAs-material. However, attempts to do so resulted in a surprising behavior of the photodiode current, which exhibits a strong dependence on the photodiode voltage, in particular with increasing output power of the VCSEL. This unexpected behavior is undesired. Another undesired effect is an increased capacity of the InGaAs-based photodiode. It was found to be advantageous in a ViP in which the active region as well as the light absorption region are based on the InGaAs material system to provide the InGaAs layer in the light absorption region with an indium content which is higher than the indium content in the active region.

The higher indium content in at least one InyGa<NUM>-yAs layer of the light absorption region further advantageously increases the light absorption by the photo detector.

A difference y - x between indium content of the InGaAs-layer(s) in the light absorption region and indium content of the InGaAs-layer(s) in the active region may be in a range from <NUM> to <NUM>. Preferably, the difference y - x may be in a range from <NUM> to <NUM>. More preferably, the difference y - x may be in a range from <NUM> to <NUM>.

The active region of the optical resonator may comprise one or more quantum wells comprising one or more InxGa<NUM>-xAs layers. x may be zero, i.e. the active region may comprise one or more GaAs layers. In other embodiments, x may be greater than zero, i.e. <NUM> < x < <NUM>. Each quantum well may comprise an InxGa<NUM>-xAs layer sandwiched between semiconductor layers having a larger band gap than the InxGa<NUM>-xAs layer.

The photodiode may be monolithically integrated with the VCSEL. In particular, the photodiode may be arranged in the optical resonator to form an intracavity monolithically integrated photodiode. Preferably, the photodiode may be incorporated into the first or second DBR. The InyGa<NUM>-yAs layer of the light absorption region is preferentially undoped. The InyGa<NUM>-yAs layer may thus form an intrinsic layer of a p-i-n photodiode structure which advantageously reduces the capacity of the photodiode.

The light absorption region of the photodiode comprises at least one further undoped layer, wherein the InyGa<NUM>-yAs layer is immediately adjacent to the further layer. In combination with an intrinsic InyGa<NUM>-yAs layer of the light absorption region the intrinsic zone of the light absorption region may be thus increased which further helps to reduce the strong dependence of the photo current on the photodiode voltage and to reduce the capacitance of VCSEL.

Further, adding one or more intrinsic layers in the light absorption region based on a material different from the InyGa<NUM>-yAs layer is advantageous in comparison with increasing the thickness of the InyGa<NUM>-yAs layer, because the thickness of the InyGa<NUM>-yAs layer is limited by conditions for the epitaxial growth which does not allow thick layers with high indium content due to strain.

The at least one further undoped layer in the light absorption region of the photodiode is a GaAszP<NUM>-z layer with <NUM> < z < <NUM>. z may be <NUM>, for example. GaAszP<NUM>-z is advantageous as it partially compensates strain in the InGaAs-layer.

Further preferentially, the light absorption region of the photo detector may comprise at least two undoped (e.g. undoped GaAs or undoped GaAszP<NUM>-z) layers, wherein the InyGa<NUM>-yAs layer is sandwiched by the further layers.

In an example not falling under the scope of the claims, the light absorption region may comprise a single InyGa<NUM>-yAs layer.

Further preferentially, the light absorption region may comprise at least two InyGa<NUM>-yAs layers separated by at least one undoped further layer. In this way, the absorption of the photo detector can be advantageously further increased. The further layer is, in accordance with the invention, an undoped GaAszP<NUM>-z layer.

The at least one InyGa<NUM>-yAs layer of the light absorption region may have a thickness in range from <NUM> - <NUM>. The maximum thickness of the InyGa<NUM>-yAs layer which meets the conditions for epitaxial growth depends on the indium content of the InyGa<NUM>-yAs-layer. The higher the indium content of the InyGa<NUM>-yAs layer, the less is the maximum thickness suitable for epitaxial growth of the layer stack. For example, for y being about <NUM> (<NUM>% indium content), a practical limit of the thickness of an InyGa<NUM>-yAs-layer would be <NUM> - <NUM>.

An intrinsic zone of the light absorption region has a total thickness of at least <NUM>, preferably of at least <NUM>, further preferably of at least <NUM>. As indicated above, a thicker intrinsic zone of the light absorption region may further help to reduce the strong dependence of the photo current on the photodiode voltage and reduce the capacitance of the VCSEL.

One of the DBRs may have a first part and a second part, wherein the light absorption region including the InyGa<NUM>-yAs layer maybe arranged between the first part and the second part of that DBR. The one part of the first and second parts which is arranged closer to the active region than the other part of the DBR preferentially has at least two DBR layer pairs with different refractive indices, or may have four or even more DBR layer pairs.

The electrical contact arrangement may comprise a contact layer arranged between the active region and the light absorption region. The contact layer may be an n-contact layer. The contact layer is advantageous as it solves or at least reduces surface non-uniformity problems caused when etching the epitaxial layer stack down to the substrate for making the electrical contact, and also solves the problem of electrical contact resistance, when etching only down to a functional layer and making the electrical contact on the functional layer. In case the contact to be made is an n-contact, the contact layer may be an n-doped, low aluminum containing but still transparent layer. The contact layer may be thick enough to overcome the non-uniformity problem of the etching process. The contact layer may be arranged in the first or second DBR. In this case, the optical thickness of the contact layer should be an integer multiple of λ/<NUM> so that the DBR is effectively divided into two parts by the contact layer, which two parts have reflectivity that add up in a constructive way. The phase of each DBR part is thus in-phase.

Further according to the invention, an optical sensor is provided, comprising a Vertical Cavity Surface Emitting Laser device according to any of the above embodiments.

The optical sensor may be comprised by a mobile communication device.

The optical sensor may be used for distance detection, velocity detection, particle density detection, gesture control, and especially for all sensor applications which are based on self-mixing interference measurements.

Further according to the invention, a method of producing a Vertical Cavity Surface Emitting Laser device is provided, as defined in claim <NUM>.

The steps of the method need not be performed in the order given. The different layers of the first and second DBRs, the active region and the photo detector may be deposited by epitaxial methods like MOCVD, MBE and the like.

The VCSEL device may comprise a substrate onto which the layer stack of the VCSEL with integrated photodiode is grown. The substrate may be removed after the VCSEL device is produced.

The VCSEL device may be a top emitter or a bottom emitter.

It shall be understood that the VCSEL device according to any embodiment described above and the method of producing the VCSEL device have similar and/or identical embodiments, in particular, as defined in the independent claim. Further advantageous embodiments are defined below.

It shall be understood that the preferred embodiment of the invention can also be any combination of the dependent claims with the respective independent claims.

In the following drawings:.

In the following description, embodiments of a Vertical Cavity Surface Emitting Laser device with monolithically integrated photodiode (ViP) based on the InGaAs material system will be described. Conventionally, ViPs are based entirely on the AlGaAs material system to provide laser emission at a wavelength of about <NUM>, with quantum wells based on GaAs or AlGaAs and a photodiode based on GaAs. Using the AlGaAs material system, much longer emission wavelengths than <NUM> are not possible. Using InGaAs material may solve this problem in view of the lower band gap of InGaAs in comparison with the band gap of AlGaAs. It appears to be straight forward to replace a GaAs-photodiode by a similar one based on InGaAs material. However, a surprising behavior of the photodiode current (PD current) was observed. The PD current may exhibit a strong dependence on the photodiode voltage U_PD. <FIG> shows this surprising behavior of the PD current as function of the photodiode voltage U_PD for several output powers Pout of the VCSEL from <NUM> mW to <NUM> mW for a photodiode based on InGaAs and an emission wavelength of <NUM>. The voltage-dependence of the photodiode current is the more significant the higher the output power of the VCSEL is.

The present invention proposes a VCSEL with monolithically integrated photodiode, in which both the active region of the VCSEL as well as the photodiode are based on the InGaAs material system for light emission and detection, preferably in a wavelength range from <NUM> to <NUM>.

<FIG> shows a first embodiment of a VCSEL device <NUM> according to the principles of the invention. The VCSEL device <NUM> comprises a first distributed Bragg reflector (DBR) <NUM>, an active region <NUM> for laser light emission, and a second distributed Bragg reflector (DBR) <NUM>. The active region <NUM> is arranged between the first and second DBRs <NUM>, <NUM>. The first DBR <NUM>, the active region <NUM> and the second DBR <NUM> form an optical resonator <NUM>. The VCSEL device <NUM> further comprises a photodiode <NUM> having a light absorption region <NUM>.

The layer stacks of the first DBR <NUM>, the active region <NUM>, the second DBR <NUM> and the light absorption region <NUM> of the photodiode may be epitaxially grown on a substrate <NUM>. The layers of the first and second DBRs <NUM>, <NUM> may comprise doped AlGaAs material.

In case the VCSEL device <NUM> is a top emitter, the first DBR <NUM> may be partly transmissive for the laser radiation generated in the active region <NUM>. The laser light is emitted by the VCSEL device <NUM> as illustrated by an arrow <NUM>. The first DBR <NUM> may have a reflectivity of about <NUM>%, for example. The second DBR <NUM> may have a reflectivity of ≥ <NUM>%. It is to be understood that in other embodiments, the VCSEL device <NUM> may be configured as a bottom emitter, i.e. laser light is emitted on the substrate side of the VCSEL device <NUM>, wherein the reflectivity of the first DBR <NUM> may be ≥ <NUM>% and the reflectivity of the second DBR <NUM> may be about <NUM>% in case of a bottom emitter. The substrate <NUM> may be removed in further embodiments. In further embodiments, the light absorption region <NUM> may be arranged in the top of the second DBR <NUM>. In still further embodiments, the light absorption layer <NUM> may be arranged in the first DBR <NUM> of a top emitter or in the second DBR <NUM> of a bottom emitter.

Each of the first and second DBRs <NUM>, <NUM> may have one or more layer pairs, wherein each layer pair has different indices of refraction. The number of layers shown in <FIG> is only schematic and exemplary and not limiting. The thickness of the layers shown in <FIG> is not to scale and only schematic and exemplary.

The optical resonator <NUM> may further comprise one or more oxide apertures (not shown) in the VCSEL of the VCSEL device.

The light absorption region <NUM> of the photodiode <NUM> is embedded in the second DBR <NUM>, thus dividing the second DBR <NUM> in a first part <NUM> and a second part <NUM>.

The substrate <NUM> and the second part <NUM> of the second DBR <NUM> may be n-doped. The first part <NUM> of the second DBR <NUM> may have an n-doped first region <NUM>, an n-doped second region <NUM>, and a p-doped third region <NUM>. The n-doped second region <NUM>, the p-doped third region <NUM>, the light absorption region <NUM>, which preferably is an intrinsic (undoped) region, and the n-doped second part of the second DBR <NUM> build up the photodiode <NUM>. Thus, the photodiode <NUM> may be an n-p-i-n photodiode formed by the light absorption region <NUM> and the layers of the regions <NUM>, <NUM>, <NUM> of the second DBR <NUM>.

The VCSEL device <NUM> further comprises an electrical contact arrangement, which may comprise a p-contact <NUM> on top of the first DBR <NUM>, an n-contact <NUM> on the bottom of the substrate <NUM>, and a further n-contact <NUM> on top of the region <NUM> of the second DBR <NUM>. The p-contact <NUM> may be formed as a ring electrode. The p-contact <NUM> may be arranged on a cap layer (not shown) on top of the first DBR <NUM>. The n-contact <NUM> may be formed as a metallization of the bottom of the substrate <NUM>. In case the VCSEL device <NUM> is designed as a bottom emitter, the n-contact <NUM> may be formed as a ring electrode.

The p-contact <NUM> may form the anode of the VCSEL, and the n-contact <NUM> may form the cathode of the VCSEL. At the same time, the n-contact <NUM> may form the anode of the photodiode <NUM>, while the n-contact <NUM> may form the cathode of the photodiode <NUM>.

The active region <NUM> comprises at least one InxGa<NUM>-xAs layer, wherein <NUM> ≤ x < <NUM>. In an example, x may be <NUM>, thus the InxGa<NUM>-xAs layer may be of a composition In<NUM>Ga<NUM>As, therefore containing <NUM>% indium in this example. In<NUM>Ga<NUM>As may provide laser emission at about <NUM> at a temperature of about <NUM>. Longer wavelengths may be obtained by using InGaAs material with higher indium content, x may be in a range from <NUM> or <NUM> to <NUM>, for example to achieve laser light emission in a desired wavelength range. The photoluminescence peak of the active region <NUM> with In<NUM>Ga<NUM>As is at a shorter wavelength than the emission wavelength of the VCSEL and may be at about <NUM>. The active layer <NUM> may comprise several quantum wells of InxGa<NUM>-xAs of only several nm thickness. For example, a thickness in a range from <NUM> to <NUM>, e.g. a thickness of <NUM> may be appropriate. x may be zero, i.e. the active region may comprise one or more GaAs quantum wells.

The light absorption region <NUM> of the photodiode <NUM> also comprises at least one InyGa<NUM>-yAs-layer. The indium content of the InyGa<NUM>-yAs-layer is higher than the indium content of the InxGa<NUM>-xAs-layer, and may be, in the above example of an In<NUM>Ga<NUM>As active region <NUM>, an In<NUM>Ga<NUM>As-layer, thus having an indium content of about <NUM> %.

In general, a difference y - x of the indium content of the InGaAs-layers in the active region <NUM> and the light absorption region may be in a range from <NUM> to <NUM>, preferably in a range from <NUM> to <NUM>, further preferably in a range from <NUM> to <NUM>.

A single InyGa<NUM>-yAs-layer in the light absorption region <NUM> has a thickness in a range from <NUM> - <NUM>. The maximum thickness of the InyGa<NUM>-yAs layer is limited by conditions for the epitaxial growth which do not allow thick layers with high indium content due to strain. A practical limit would be <NUM> - <NUM> for the above example of an indium content of about <NUM>%.

While in an example not according to the invention as claimed, the light absorption region <NUM> of the photodiode <NUM> may be just made of a single thin intrinsic InGaAs-layer, a thicker intrinsic zone may be used as the light absorption region <NUM> in a preferred embodiment.

<FIG> shows such an embodiment of the light absorption region <NUM> embedded between the p-doped third region <NUM> of the second DBR <NUM> and the n-doped second part <NUM> of the second DBR <NUM>. The third region <NUM> and the second part <NUM> are only shown in part in <FIG>. As shown in <FIG>, the light absorption region <NUM> of the photodiode <NUM> comprises an intrinsic zone comprising two intrinsic InGaAs-layers which may have an indium content of <NUM>%, for example. The intrinsic zone further comprises three further undoped layers which in this example may comprise undoped GaAs-layers. Thus, undoped material, e.g. GaAs, which is not in accordance to the present invention as claimed, or GaAszP<NUM>-z with z = <NUM>, is preferably added around one or more InGaAs-layers such that the total thickness of the intrinsic material is at least <NUM>, more preferred <NUM>, and even more preferred <NUM>. Such a thick intrinsic zone might seem to be counter-intuitive, but the thicker intrinsic zone can help to reduce the strong dependence of the photocurrent on the photodiode voltage and to reduce the capacitance of the VCSEL. Further, using more than one InGaAs-layers for the light absorption region <NUM> helps to increase the absorption of the photodiode <NUM>. In the present invention as disclosed in the claims, using GaAsP instead of GaAs for the layers in the intrinsic zone has the additional advantage that the strain that has built up in the InGaAs-layer is partially compensated.

The InGaAs-layer or layers may be arranged alternating with the further undoped layers as shown in <FIG> so that an InGaAs-layer is embedded or sandwiched between two undoped further layers and immediately adjacent to the undoped further layers.

Returning to <FIG>, the third portion <NUM> of the first part <NUM> of the second DBR <NUM> preferably comprises at least <NUM> DBR layer pairs, more preferred <NUM> or even more DBR layer pairs. This may further reduce the voltage-dependence of the photodiode current.

The transition between the third portion <NUM> and the first portion <NUM> of the first part <NUM> of the second DBR is preferably designed such that the last p-doped layer of the third region <NUM> is with a high aluminum content or a layer where the aluminum content is gradually decreased from high values to low values.

<FIG> shows a further embodiment of a VCSEL device <NUM>, wherein elements of the VCSEL device <NUM> in <FIG> which are identical, similar or comparable with respective elements of the VCSEL device <NUM> in <FIG> are denoted with the same reference numerals.

The difference between the VCSEL device <NUM> in <FIG> and the VCSEL device <NUM> in <FIG> is a contact layer <NUM> between the first region <NUM> and the second region <NUM> of the first part <NUM> of the second DBR <NUM>. The contact layer <NUM> is an n-contact layer. The optical thickness of the contact layer <NUM> preferably is an integer multiple of λ/<NUM> so that the second DBR <NUM> is effectively divided into two sections (regions <NUM> and regions <NUM>, <NUM> and <NUM>) which have reflectivity that add up in a constructive way. The phase of each of the DBR sections is in-phase so that not a second resonator is formed.

The contact layer <NUM> may have a low aluminum content, but is still transparent to the light emitted by the VCSEL.

The term "intrinsic layer", "intrinsic zone" or "intrinsic material", etc. as used herein is to be understood as being a layer, zone or material which is without any significant dopant species level present in the layer, zone or material. The same holds for the term "undoped" which means not having any significant dopant species level.

<FIG> shows a sketch of an optical sensor <NUM> according to an embodiment. The optical sensor <NUM> is arranged to determine presence, distances and movements of objects by means of self-mixing interference measurements. The optical sensor <NUM> comprises a VCSEL device <NUM> as described above, a transmission window <NUM> and a driving circuit <NUM> for electrically driving the VCSEL device <NUM>. The driving circuit <NUM> is electrically connected to the VCSEL device <NUM> via the contacts <NUM> and <NUM> to supply electrical power to the VCSEL device <NUM> in a defined way. The driving circuit <NUM> may comprise a memory device for storing data and instructions to operate the driving circuit <NUM>. The optical sensor <NUM> further comprises an evaluator <NUM>. The photodiode <NUM> comprised by the VCSEL device <NUM> is arranged to determine variations in the standing wave pattern within the laser cavity coupled to the respective photodiode. The evaluator <NUM> may comprise at least one memory device like a memory chip and at least one processing device like a micro-processor. The evaluator <NUM> is adapted to receive electrical signals from the VCSEL device <NUM> and optionally from the driving circuit <NUM> to determine distances or movements of one or more objects based on the interference of laser light <NUM> which is reflected by the respective objects as reflected laser light <NUM> and the optical standing wave within the optical resonator of the VCSEL (self-mixing interference). The optical sensor <NUM> may be used for particle detection, distance/velocity measurements, user interfaces, etc..

<FIG> shows a sketch of a mobile communication device <NUM> comprising an optical sensor <NUM>. The optical sensor <NUM> can, for example, be used in combination with the software application running on the mobile communication device <NUM>. The software application may use the optical sensor <NUM> for sensing applications. Such sensing applications may, for example, be self-mixing interference measurement applications, particle sensing applications or an application of a gesture based user interface.

<FIG> shows a principle sketch of a process flow of a method of producing a VCSEL device according to the present invention. In step <NUM>, a substrate (substrate <NUM> in <FIG>) is provided. In step <NUM>, the second part <NUM> of a second DBR <NUM> as described above is provided on the substrate <NUM>. In step <NUM>, a light absorption region <NUM> as described above is provided on the second part <NUM> of the second DBR <NUM>.

In step <NUM>, third and second regions <NUM> and <NUM> of a first part <NUM> of the second DBR <NUM> as described above are provided on the light absorption region <NUM>. In optional step <NUM>, a contact layer <NUM> is provided on the second region <NUM> of the first part <NUM> of the second DBR <NUM>. In step <NUM>, a first region <NUM> of the first part <NUM> of the second DBR <NUM> is provided on the second region <NUM> or the contact layer <NUM>. In step <NUM>, an active region <NUM> as described above is provided on the first region <NUM> of the first part <NUM> of the second DBR <NUM>. In step <NUM>, the optical resonator <NUM> comprising the first and second DBRs <NUM>, <NUM> and the active region <NUM> is electrically contacted as described above. In step <NUM> the photodiode <NUM> comprising the second and third regions <NUM>, <NUM> of the first part <NUM> of the second DBR <NUM>, the light absorption region <NUM> and the second part <NUM> of the second DBR <NUM> is electrically contacted as described above.

The active region <NUM> is provided comprising at least one InxGa<NUM>-xAs layer, wherein <NUM> < x < <NUM>, for light emission. The light absorption region <NUM> of the photodiode <NUM> is provided with at least one InyGa<NUM>-yAs-layer, wherein <NUM> < y < <NUM>, wherein y is greater than x.

Electrically contacting may comprise one or more steps of etching down the layer structure of the VCSEL device with an appropriate etching technology to the respective layer of the second region <NUM> of the first part <NUM> of the second DBR <NUM> or to the contact layer <NUM>. The process may further comprise an oxidation process in order to provide an oxide aperture in the VCSEL of the VCSEL device. The production process may further comprise a passivation or planarization process to provide a smooth surface for depositing bond pads. The substrate <NUM> may be removed after depositing the semiconductor layers of the VCSEL structure. The n-contact <NUM> of the photodiode <NUM> may be provided after thinning or grinding the substrate <NUM> on the thinned backside of the substrate <NUM>.

The layers of the first DBR, the active region and any other layers as current injection layers and alike may be deposited by epitaxial methods like MOCVD or MBE.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments but only by the features disclosed in the appended claims.

Claim 1:
Vertical Cavity Surface Emitting Laser device, comprising an optical resonator (<NUM>), a photodiode (<NUM>), and an electrical contact arrangement (<NUM>, <NUM>, <NUM>), the optical resonator (<NUM>) comprising a first distributed Bragg reflector (<NUM>), a second distributed Bragg reflector (<NUM>), and an active region (<NUM>) for light emission, wherein the active region (<NUM>) is arranged between the first and second distributed Bragg reflectors (<NUM>, <NUM>), wherein the photodiode (<NUM>) comprises a light absorption region (<NUM>) arranged in the optical resonator (<NUM>), and the electrical contact arrangement (<NUM>, <NUM>, <NUM>) is arranged to provide an electrical drive current to electrically pump the optical resonator (<NUM>), and to electrically contact the photodiode (<NUM>), wherein the active region (<NUM>) comprises at least one InxGa<NUM>-xAs layer, wherein <NUM> ≤ x < <NUM>, and the light absorption region (<NUM>) comprises at least one InyGa<NUM>-yAs layer, wherein <NUM>< y < <NUM>, and wherein y is greater than x, wherein the InyGa<NUM>-yAs layer of the light absorption region (<NUM>) is an intrinsic layer of the light absorption region (<NUM>), wherein the light absorption region (<NUM>) of the photodiode (<NUM>) comprises at least one undoped further layer based on a material different from the InyGa<NUM>-yAs layer, wherein the InyGa<NUM>-yAs layer is immediately adjacent to the further layer, and wherein an intrinsic zone of the light absorption region (<NUM>) has a total thickness of at least <NUM>, characterized in that:
- the at least one InyGa<NUM>-yAs layer of the light absorption region (<NUM>) has a thickness in a range from <NUM> - <NUM>, and
- wherein the at least one undoped further layer comprises GaAszP<NUM>-z, with <NUM><z<<NUM>.