JPS62283684A - Optical probe unit - Google Patents

Abstract

PURPOSE:To simply obtain an optical probe of semiconductor by introducing a probe light from the end sphere of an optical fiber incident to a semiconductor light emitting element, and observing a photovoltaic current or a photovoltaic voltage generated at the semiconductor while moving the incident position to simplify the configuration of an optical probe unit to shorten the measuring time. CONSTITUTION:A semiconductor light emitting element 1 of an article to be measured is of an InGaAsP/InP buried hetero structure semiconductor laser, and emits 1.3mum of wavelength. The radius of curvature of an end sphere 3 formed at one end of a single mode optical fiber 2 in a spherical shape is 10mum. The light emitted from a light source 4 equal in oscillation wavelength to the emitting light wavelength of the element 1 is propagated in the fiber 2, then emitted from the sphere 3, and incident as a probe light to the element 1. An optical current or voltage generated at the element 1 by the probe light is measured by a detector 5. The fiber 2 is held by a chuck 6, which is moved by a fine adjusting unit to finely move the incident position of the light to the element 1 in X and Y directions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical probe device, and particularly to an optical probe device suitable for non-destructively probing a semiconductor light-emitting element in a tube.

Collected lecture papers, volume 1, p. 171 (1985
), the light emitted from the multimode spherical fiber hermetically fixed to the semiconductor laser module is incident on the active layer of the semiconductor laser on the heat sink, and the terminal voltage of the semiconductor laser generated thereby is observed. The optical axis of the semiconductor laser and the multimode spherical fiber was adjusted.

[Problem that the invention seeks to solve]

The above-mentioned prior art relates to optical axis adjustment, and does not involve an optical probe in which light is incident on a semiconductor light emitting element and the photocurrent and photovoltage are measured to analyze the characteristics.

In order to perform an optical probe, it is not necessary to fix an optical fiber or a semiconductor light emitting element to a module as in the conventional structure, and the tipped fiber may be of a single mode.

When light with a photon energy greater than the band gap, that is, light with a wavelength equal to or shorter than the emission wavelength of the light-emitting device, enters the vicinity of the active layer of a semiconductor light-emitting device, light absorption occurs and electron-hole pairs are generated. Focusing on the minority carriers among these carriers, the minority carriers diffuse in all directions by the diffusion length on average, and then recombine with the majority carriers and disappear. However, some of the minority carriers are pn
It reaches the depletion layer formed at the junction or Peter junction, and drifts within the depletion layer due to the force of the electric field. The passage of the number carriers through the depletion layer means the generation of photocurrent. Here, if the electrodes of the light emitting element are short-circuited, the photocurrent can be measured, and if the electrodes are opened, the photoelectromotive voltage can be measured. Photocurrent and photovoltage are functions of incident light intensity, absorption rate, minority carrier concentration, diffusion constant, lifetime, etc., but their functional forms are different.

In general, photocurrent is mainly generated when the position of incident light is in a region with high absorption rate, and photovoltaic voltage is also likely to be generated in a region with low absorption rate near the junction. Therefore, more information can be obtained by measuring both photocurrent and photovoltage. In the conventional example, since the purpose was to align the optical axis, only one of the photocurrent and photovoltage was measured.

As for the photovoltaic voltage, in the conventional example, only the voltage peak value is detected, and the characteristics of the semiconductor light emitting device are not analyzed from the profile of the photovoltaic voltage with respect to the position of incident light.

An object of the present invention is to provide an optical probe device suitable for optical probing of semiconductor light emitting devices.

[Means for solving problems]

The above objective is achieved by making the probe light emitted from the tip of the optical fiber incident on the semiconductor light emitting element, and measuring the photovoltaic current or photovoltage generated in the semiconductor while moving the incident position. .

[Effect]

By optically probing a semiconductor light emitting device using the above means, a photocurrent value or a positive photovoltaic value corresponding to the position of incident light on the light emitting device can be obtained. Since the photocurrent value mainly depends on the number of carriers generated by light, information regarding the active layer of the light emitting device can be obtained. Information on the vicinity of the active layer can also be obtained from the positive photovoltaic value. In this way, useful information regarding semiconductor light emitting devices can be easily obtained in a non-destructive manner.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a first embodiment of an optical probe device according to the present invention, and FIG. 2 is a partially enlarged view of the first embodiment. 1st
In @ and FIG. 2, the semiconductor light emitting device 1 of the object to be measured is
is an InGaAsP/InP-based buried heterostructure half-groove buried laser and emits light at a wavelength of 1.3 μm. A single mode optical fiber was used as the optical fiber 2. The radius of curvature of the spherical tip portion 3, which is formed by processing one end of the optical fiber 2 into a spherical shape, is 10 μm.

The light source 4 is a semiconductor laser that oscillates at a wavelength of 1.3 μm, and its oscillation wavelength is equal to the emission wavelength of the semiconductor light emitting cord 1. After propagating, the light is emitted from the tip sphere 3 and is incident on the surface of the semiconductor light emitting device 1 as a probe light. The beam spot radius of the probe light on the surface of the semiconductor light emitting device 1 was approximately 1.5 μm, and the light power was 2 mW. The photocurrent or photovoltage generated in the semiconductor light emitting device 1 by this probe light was measured by the detector 5.

The detector 5 is electrically connected to the electrode of the semiconductor light emitting device 1 . In the case of photocurrent, the input impedance of the detector 5 was made sufficiently smaller than the resistance of the semiconductor light emitting element 1 to short-circuit the electrodes of the semiconductor light emitting element 1, and in the case of photovoltaic voltage, the input impedance of the detector 5 was made sufficiently large to create an open circuit.

The optical fiber 2 is held by a chuck 6, and the chuck 6 can be moved by a fine adjustment device (not shown). That is, the position of incidence of the probe light on the light emitting element 1 can be slightly moved in the X direction and the Y direction in FIG.

Figure 4 shows the results of measurements made in the first example6.
The detector 5 and the chuck 6 fine adjustment device shown in FIG. 1 were linked together, and the results were output by an XY recorder. The vertical axis in FIG. 3 is the photocurrent or photovoltaic voltage, and the horizontal axis is the position of incident light. The origin of X=Y=O represents the center of the active layer of the semiconductor light emitting device 1.

This example is useful for analyzing characteristics caused by the structure of a semiconductor laser. Although a single mode optical fiber is used in this embodiment, a multimode optical fiber may be used depending on the application. It is also possible to observe the optical response by changing the wavelength of the probe light, by applying a bias between the electrodes of the semiconductor light emitting device, or by using the probe light as pulsed light rather than continuous light.

FIG. 4 is a diagram showing a second embodiment of this embodiment.

A portion of the light incident on the semiconductor light emitting device 1 from the tip portion 3 is absorbed and contributes to the generation of photocurrent, and a portion is scattered.

Of this scattered light, the light that returns to the tip sphere 3 propagates through the optical fiber 2 in the opposite direction to the probe light, is reflected by the half mirror 7, and then enters the spectrometer 8. The spectrometer 8 can perform wavelength analysis of the scattered light. In this way, it was possible to simultaneously measure the photocurrent and photovoltage of the semiconductor light emitting device 1 using the optical probe device and observe light scattering signals such as Raman scattering.

According to this embodiment, a light scattering signal can be measured simultaneously in addition to a photocurrent and a photoelectromotive voltage, increasing the amount of information, so that the characteristic analysis of semiconductor light emitting devices is more effective.

〔Effect of the invention〕

According to the present invention, since the device configuration is simple and the measurement time is short, there is an advantage that optical probing of semiconductors can be performed easily.

Furthermore, since the light propagated through the optical fiber and emitted can be well approximated by a Gaussian beam, there is an effect that the theoretical analysis of the measurement results can be easily performed.

By adjusting the radius of curvature of the tip of the optical fiber and the distance between the tip and the semiconductor light emitting element, the spot size of the probe light can be narrowed down to the diffraction limit, making it suitable for local analysis of fine structures. Are suitable.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the first embodiment of the present invention, Fig. 2 is a partially enlarged view of the first embodiment, Fig. 3 is a diagram showing measurement results of the first embodiment, and Fig. 4 is a diagram showing the measurement results of the first embodiment. It is a figure showing a 2nd example. 1... Semiconductor light emitting device, 2... Optical fiber, 3...
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Claims (1)

[Claims] 1. In an optical probe device that uses a semiconductor light emitting device as an object to be measured and is composed of an optical fiber and a light source, the optical fiber has a spherical tip at one end, and the light from the light source is The wavelength is equal to or shorter than the wavelength of the light of the semiconductor light emitting element, and the probe light is emitted from the light source, propagates within the optical fiber, and is emitted from the tip bulb, and the probe light is made to enter the semiconductor light emitting element as an optical probe light. An optical probe device, characterized in that a photocurrent or photovoltage generated in the semiconductor light emitting element is observed while moving its incident position.