Experimental facts about noise are presented which help us to understand the correlation between noise in a device and its reliability. The main advantages of noise measurements are that the tests are less destructive, faster and more sensitive than DC measurements after accelerated life tests. The following topics are addressed: 1) the kind of noise spectra in view of reliability diagnostics such as thermal noise, shot noise, the typical poor-device indicators like burst noise and generation-recombination noise and the 1/f/sup 2/ and 1/f noise; 2) why conduction noise is a quality indicator; 3) the quality of electrical contacts and vias; 4) electromigration damage; 5) the reliability in diode type devices like solar cells, laser diodes, and bipolar transistors; and 6) the series resistance in modern short channel MESFET, MODFET, and MOST devices. >

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Noise as a diagnostic tool for quality and reliability of electronic devices

Published data on the properties of metal-semiconductor ohmic contacts and mechanisms of current flow in these contacts (thermionic emission, field emission, thermal-field emission, and also current flow through metal shunts) are reviewed. Theoretical dependences of the resistance of an ohmic contact on temperature and the charge-carrier concentration in a semiconductor were compared with experimental data on ohmic contacts to II–VI semiconductors (ZnSe, ZnO), III–V semiconductors (GaN, AlN, InN, GaAs, GaP, InP), Group IV semiconductors (SiC, diamond), and alloys of these semiconductors. In ohmic contacts based on lightly doped semiconductors, the main mechanism of current flow is thermionic emission with the metal-semiconductor potential barrier height equal to 0.1–0.2 eV. In ohmic contacts based on heavily doped semiconductors, the current flow is effected owing to the field emission, while the metal-semiconductor potential barrier height is equal to 0.3–0.5 eV. In alloyed In contacts to GaP and GaN, a mechanism of current flow that is not characteristic of Schottky diodes (current flow through metal shunts formed by deposition of metal atoms onto dislocations or other imperfections in semiconductors) is observed.

Mechanisms of current flow in metal-semiconductor ohmic contacts

We review recent advances in subwavelength high-index-contrast gratings (HCGs) and a variety of applications in optoelectronic devices, including vertical-cavity surface-emitting lasers (VCSELs), tunable VCSELs, high-Q optical resonators, and low-loss hollow-core waveguides (HWs). HCGs can serve as broadband (Delta lambda/lambda ~ 35%), high-reflectivity (>99%) mirrors for surface-normal incident light, which is useful to replace conventional distributed Bragg reflectors in optical devices. HCGs can also be designed as high-Q resonators with output coupling in the surface-normal direction. Finally, we discuss a novel design of HCG as shallow angle reflectors and HWs.

High-Index-Contrast Grating (HCG) and Its Applications in Optoelectronic Devices

Signal processing and calibration procedures for in situ diode-laser absorption spectroscopy.

A diode-pumped broadband multiple-quantum-well vertical-external-cavity surface-emitting semiconductor laser has been developed for high-sensitivity intracavity laser-absorption spectroscopy. The semiconductor structure design has been optimized so as to provide maximum laser-emission bandwidth and wavelength tunability. The laser has a 100-mW threshold of continuous room-temperature operation, and it can be tuned within 25 nm around its design wavelength (980 nm). A detection limit lower than 10-10 per centimeter of absorption path has been achieved, given ∼3×10-11 cm-1 Hz-1/2. Its spectro-temporal dynamics has been studied in the time range from a few microseconds to ∼1 s. No evidence of nonlinear mode interactions, which in many cases limit the sensitivity, has been observed. We have also shown that with a cavity length reduced to 2.5 cm, the laser is very attractive as a tunable single-frequency source owing to its stable operation in a single TEM00 mode at a pump power of up to 1 W.

Diode-pumped broadband vertical-external-cavity surface-emitting semiconductor laser applied to high-sensitivity intracavity absorption spectroscopy

Trace gas detection with antimonide-based quantum-well diode lasers.

Monolithic Sb-based vertical cavity surface emitting lasers (VCSELs) operating near 2.2 /spl mu/m at room temperature have been successfully fabricated and characterised. A pulsed output optical power of 20 mW has been achieved, the threshold current density being 2 kA/cm/sup 2/ for 200 /spl mu/m diameter devices. The entire structure was grown in a single growth run using molecular beam epitaxy.

Sb-based monolithic VCSEL operating near 2.2 [micro sign]m at room temperature

Ohmic contacts on GaSb were achieved using ZnAu multilayers for p-type GaSb and TeAu multilayers for n-type GaSb. Contacts were electrically characterized by their specific resistance, which could be obtained currently as low as 10−5 Ω cm2 for p-type GaSb and 10−6 Ω cm2 for n-type GaSb. The surface composition was studied by means of secondary ion mass spectrometry, which showed that interface alloying gives the best results.

Characterization of ohmic contacts on n- and p-type GaSb

Several metallization systems for producing ohmic contacts onto GaSb have been investigated. The minimization of contact resistivity was respectively obtained with Au-Zn on p type and Au-Te on n type. It has been shown that these results are due to an overdoped layer at the semiconductor surface. Low frequency noise measurements pointed out that the techniques used allow the realization of devices without 1/f contact noise

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Low noise ohmic contacts on n and p type GaSb

The fabrication of the first optically pumped GaSb-based VCSELs emitting in the 2-2.5 /spl mu/m is described. The typical structure was fabricated in two steps: a growth by molecular beam epitaxy (MBE) on GaSb substrate, and an evaporation of dielectric materials. First, a bottom lattice-matched semiconductor GaSb/AlAsSb Bragg mirror followed by a one-wavelength cavity containing a type I multiquantum-well Ga/sub 0.65/In/sub 0.35/As/sub 0.1/Sb/sub 0.9//Al/sub 0.35/Ga/sub 0.65/ As/sub 0.1/Sb/sub 0.9/ were MBE-grown. Then, after a whole characterisation of this 1/2 structure, a top-evaporated dielectric Bragg mirror of 10 pairs of YF/sub 3//ZnS was deposited to complete the VCSEL structure. This process allowed the fabrication of optically pumped VCSELs emitting near 2.3 /spl mu/m and operating in quasi-CW (10 /spl mu/s, 2kHz) regime at around 100 K. The threshold intensity was as low as 1.3 kW/cm/sup 2/ and the measured output power 0.8 mW The tunability was about 100 nm and the laser linewidth <0.9 nm.

Sophie Gaillard

Papers

Trace gas detection with antimonide-based quantum-well diode lasers.

Sb-based monolithic VCSEL operating near 2.2 [micro sign]m at room temperature

Characterization of ohmic contacts on n- and p-type GaSb

Low noise ohmic contacts on n and p type GaSb

Type-I quantum-well VCSEL structure on GaSb emitting in the 2-2.5 /spl mu/m range