JP2003215039A - PHOTOLUMINESCENCE MEASURING APPARATUS AND Si FILTER - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoluminescence measuring apparatus by which an emission spectrum from a sample at an emission wavelength peak of 1.1 μm or less can be observed. <P>SOLUTION: The photoluminescence measuring apparatus comprises a laser light source 1 by which the sample 6 is irradiated with a laser beam oscillated at a wavelength of 960 nm or less, a photodetector 10 which receives light emitted from the sample 6 and the Si filter 8 which is installed on an optical path between the sample 6 and the photodetector 10 and whose thickness is 0.4 mm or less. In a nondestructive evaluation (Fig. A), a laser diode (LD) at an excitation wavelength of 920 to 960 nm and the Si filter whose thickness is 0.1 to 0.4 mm are used in the case of an InP-based DH crystal, and an LD at an excitation wavelength of 960 nm and the Si filter whose thickness is 0.1 to 0.4 mm are used in the case of a GaAs-based DH crystal. When the excitation wavelength is 920 nm or less, the Si filter whose thickness is 0.1 mm can be used. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal light emission such as an InGaAsP layer or a strained MQW layer that emits light in the vicinity of 1 μm in an optical element crystal having a double hetero structure formed on a substrate such as InP or GaAs. The present invention relates to a photoluminescence measuring device capable of directly exciting a layer and detecting an emission spectrum from the layer to a short wavelength side as close as possible to the composition of a measurement sample with high sensitivity.

It also relates to a Si filter used in the photoluminescence measuring device.

[0003]

2. Description of the Related Art Photoluminescence measurement (PL) in a strongly excited state of a crystal grown on an InP substrate has a wavelength of 1.
A YAG laser that oscillates at 06 μm was generally used as the excitation light source. Particularly, in a crystal of a semiconductor laser for a long wavelength band, the active layer has a so-called double hetero (DH) structure in which the active layer is sandwiched by InP layers. Therefore, a YAG laser capable of directly exciting the active layer through the InP layer is used. The PL used was very effective as a means for directly evaluating the crystal quality of the active layer in a nondestructive manner. Since strong excitation can create a carrier generation state close to current injection in the active layer, it is possible to predict the threshold value and oscillation wavelength after laser processing from the emission intensity and PL spectrum from that state. Since the laser manufacturing process after crystal growth is a time-consuming step,
Since the inspection by the nondestructive measurement can reduce the process loss, it greatly contributes to increase the process yield.

[0004]

As described above,
PL measurement of the DH layer using strongly excited YAG as a light source was very useful for evaluation of crystals for long wavelength band semiconductor lasers.
However, in the conventional device, there is a limit of the detection wavelength at 1.1 μm due to the balance between the excitation wavelength and the filter for cutting it, and the wavelength composition is 1.1 μm.
It was a situation where the light emission characteristics in the shorter part could not be evaluated. Simultaneous evaluation of the compositions of the active layer, the optical signal control layer, and the optical waveguide layer will be an indispensable technique for developing future integrated optical devices. Although there are many obstacles that must be solved to realize a high-performance evaluation device for this purpose, the present device aims to provide means for radically solving these problems.

In particular, it is an object of the present invention to provide a photoluminescence measuring device and a filter used therefor, which makes it possible to observe an emission spectrum from a sample having an emission wavelength peak of 1.1 μ or less.

[0006]

A photoluminescence measuring apparatus according to the present invention comprises a laser light source for irradiating a sample with laser light oscillating at a wavelength of 960 nm or less, and a light receiver for receiving light emitted from the sample. And a Si filter having a thickness of 0.4 mm or less provided on the optical path between the sample and the light receiver.

Si for photoluminescence measurement of the present invention
The filter is made of Si and has a thickness of 0.4 mm or less.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described more specifically with reference to Examples.

FIG. 1 is a diagram showing an outline of the apparatus configuration of the present invention. Output light from a laser light source (for example, semiconductor laser) 1 having an oscillation wavelength of 1 μm is guided to an optical fiber 2 directly or via a condenser lens. Optical fiber 2
The laser light emitted from the collimator lens 3 is collimated, passes through the half mirror 4, and then is condensed by the condenser lens 5 as shown in A of FIG. 1 (InP layer 11 / light emitting layer 12).
/ InP substrate 13) structure (InP system), or
It is formed on the GaAs substrate 16 as shown in B (Al
The GaAs layer 15 / light emitting layer 14 / AlGaAs layer 15) (GaAs type) sample (so-called DH structure sample) 6 is irradiated so as to form spots on the surface of the sample 6.

The InP system and the GaAs system may be interchanged in the sample configurations of A and B, but the excitation wavelength in the case of the A type is limited to 920 to 960 nm for the InP system and 870 to 960 nm for the GaAs system. It By using such a laser beam irradiation system, it is possible to irradiate the sample while narrowing the spot system to about 1 micron while maintaining a strong laser beam output.

The laser oscillated by the semiconductor laser 1 passes through the upper InP layer 11 in the case of FIG.
The rest is absorbed by (usually of InGaAsP composition) and is not absorbed, and passes through the InP substrate 13 to be emitted to the outside.

In the case of FIG. 1B, the light emitting layer 14 appearing on the end face.
The laser is directly irradiated (made of, for example, strain MQW). In this case, the strong laser light of 920 to 960 nm, which is close to the crystal composition, penetrates into the inside relatively and has a high intensity of PL.
Cause

The photoluminescence (PL) light generated in the light emitting layer of the sample 6 is collected by the same lens 5 as that used for condensing at the time of laser irradiation, the optical path is bent to the light receiving side by the half mirror 4, and the light is excited. S to cut the light
After passing through the i-filter 8, it is guided to the optical fiber 2 ′ by the lens 9. The relationship between the Si filter and the excitation wavelength will be described in detail later.

The output from the fiber is recognized as a PL spectrum from the sample by a spectrum measuring device (light receiver) 10 such as an optical spectrum analyzer. The sample 6 is set on the pulse stage 7 and the stage is automatically moved using a personal computer, etc., and at the same time, the spectrum is also automatically acquired, so that the in-plane distribution of the PL characteristics such as the peak wavelength and the half width is automatically measured. It is also possible, and such an automated device is common.

It should be noted that by measuring the PL light emitted from the fiber by means of a highly sensitive multi-channel type photodetector after the light is dispersed, it is possible to greatly reduce the measuring time, especially in multipoint measurement.

(Conventional Example and Reference Example) FIGS. 2 and 3 show the case where PL spectra were measured by conventional YAG excitation using the same system to explain the superiority of the present invention (FIG. 2: Conventional example). , A result when measured using a semiconductor laser oscillating at 980 nm (FIG. 3: reference example). In either case, the absorption characteristic of the Si filter for cutting the excitation light (FIG. 4) is an important point for accurate spectrum measurement. In YAG excitation, in order to obtain a PL spectrum with excitation light completely cut off, Si having a thickness of 20 mm is required. On the other hand, in the case of 980 nm laser excitation, the excitation light is completely cut off with a thickness of 2 mm. The thickness of Si is sensitively reflected in its absorption characteristics as shown in FIG. S used here
Both sides of i are mirror-polished, and the transmission characteristics on the long wavelength side from the absorption edge are almost flat. This is a characteristic that is practically superior in combination with the characteristic of thickness because the spectrum can be easily corrected as compared with the case where a filter such as a multilayer film has an interference characteristic.

(Embodiment) In the configuration of A of FIG.
Using a laser oscillating at 920 to 960 nm, which is shorter than 0 nm, as an excitation light source, and performing a spectrum measurement with a 0.4-mm-thick double-sided mirror-polished Si filter, an emission wavelength peak as shown in FIG. Is 1.1 μm
It becomes easy to observe the emission spectrum from the sample as described below. As is clear from FIG. 4, the excitation wavelength and the thickness of the Si filter can sufficiently exhibit their characteristics in a very limited wavelength range. That is, the excitation wavelength 920 to 920
The thickness of the Si filter is 0.1 to 960 nm.
Very effective at 0.4 mm. High output from these lasers (100-500 mW excitation) combined with wavelength characteristics
By utilizing the characteristics, the PL emission characteristics of the DH crystal having the laser structure can be reflected in the estimation of the device characteristics.

For example, the PL intensity and the laser oscillation threshold value are as shown in FIG. That is, the higher the PL intensity, the better the quality of the crystals, and the smaller the threshold value.

Also in the configuration of FIG. 1B, the same combination of the excitation light source and the Si filter is used as shown in FIG.
The PL spectrum around μm can be observed.

In the non-destructive evaluation (in the case of A in FIG. 1), InP-based (InP / light-emitting layer / InP) DH crystal was 92.
Excitation wavelength of 0-960 nm and Si of 0.1-0.4 mm
Using a filter, GaAs-based (AlGaAs / light-emitting layer / AlGaAs) DH crystal 870-960 mmL
Use a D and 0.1-0.4 mm Si filter.

If the excitation wavelength is 920 nm or less, a 0.1 mm Si filter can be used.

[0022]

According to the photoluminescence measuring device of the present invention, the following effects can be obtained.

It has been difficult to evaluate crystals up to 1.0 to
It becomes possible to perform photoluminescence evaluation of a double hetero structure formed on InP, for example, which has an emission peak at 1.1 μm.

When a multi-channel type photodetector is used as the photodetector, the measurement time can be greatly shortened, especially in multipoint measurement.

In addition, the device of the present invention uses a sample having an emission wavelength peak of 1.1 μm or less (for example, InP) as a sample.
/ InGaAsP / InP or AlGaAs / Strain MQW /
A sample having a double edge structure made of AlGaAs)
It has a particularly remarkable effect on the measurement of.

Si for photoluminescence measurement of the present invention
According to the filter, the photoluminescence measuring device can be realized.

Both sides of the Si filter are mirror-polished, and the transmission characteristics on the long wavelength side from the absorption edge are flat, whereby the spectrum can be easily corrected.

[0028]

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a device configuration according to an embodiment.

FIG. 2 is a PL spectrum diagram of a YAG-excited 1.55DH crystal.

FIG. 3 PL of 1.55 DH crystal excited by 980 LD
It is a spectrum figure.

FIG. 4 is a transmission spectrum diagram of Si plate filters having various thicknesses.

FIG. 5 is a PL spectrum diagram of 1.08 DH by 950 LD excitation.

FIG. 6 is a graph showing the relationship between PL intensity and LD threshold.

FIG. 7 is a PL spectrum diagram of a 1 μm band strain MQW crystal excited by 920 LD.

[Explanation of symbols]

1 Semiconductor laser (laser light source) (920-1000n
2) 2'Optical fiber 3 Lens 4 Half mirror 5 Condenser lens 6 Sample 7 Pulse stage 8 Si filter 9 Lens 10 Optical emission spectrum measuring device (photodetector) such as optical spectrum analyzer 11 InP layer 12, 14 Light emitting layer 13 InP substrate 15 AlGaAs layer 16 GaAs substrate A InP / light emitting layer / InP structure B AlGaAs / light emitting layer / AlGaAs structure

Claims (7)

[Claims] 1. A laser light source for irradiating a sample with laser light oscillating at a wavelength of 960 nm or less, a light receiver for receiving light emitted from the sample, and an optical path between the sample and the light receiver. A photoluminescence measuring device, comprising: a Si filter having a thickness of 0.4 mm or less. 2. The photoluminescence measuring device according to claim 1, wherein the photodetector is a multi-channel photodetector. 3. The sample has an emission wavelength peak of 1.1 μm.
The photoluminescence measuring device according to claim 1, wherein the photoluminescence measuring device is a sample having a size of m or less. 4. The photoluminescence measuring device according to claim 1, wherein the sample is a sample having a double heterostructure consisting of InP / light emitting layer / InP. 5. The sample is AlGaAs / light emitting layer (strain MQW) / AlGaAs or GaAs / light emitting layer / GaA.
4. The photoluminescence measuring device according to claim 1, wherein the sample is a sample having a double heterostructure consisting of s and is measured so as to excite only the light emitting layer. 6. Si for photoluminescence measurement, which is made of Si and has a thickness of 0.4 mm or less.
filter. 7. The Si filter for photoluminescence measurement according to claim 6, wherein both surfaces of the Si filter are mirror-polished, and the transmission characteristics on the long wavelength side from the absorption edge are flat. .