Fiber Optic Tutorials
Broad-Area Lasers
This is continuation from the previous tutorial - what is strained-layer epitaxy. Introduction Semiconductor lasers operating in the wavelength range of 1.1-1.65 μm can be fabricated using the InGaAsP quaternary material which has been grown lattice-matched on an InP substrate. Room-temperature continuous operation of InGaAsP-InP double-heterostructure lasers was first reported in 1976. Since then, a large number of laser structures have been developed guided by the performance requirements of specific applications. The next few tutorials discuss different InGaAsP laser structures with particular emphasis on their performance in terms of the light-current characteristics, the threshold current, and the threshold current's temperature...
What is Strained-Layer Epitaxy?
This is a continuation from the previous tutorial - material parameters of InGaAsP quaternary alloy grown on InP. Although the growth of lattice-matched layers is very important for the fabrication of reliable semiconductor lasers, it is possible to make high-quality semiconductor lasers using materials with a small degree of lattice mismatch among them. This lattice mismatch introduces strain on the epitaxial layers, altering the semiconductor band structure. Typical values of tolerable strain (\(\Delta{a}/a\), where \(a\) is the lattice constant of the substrate and \(\Delta{a}\) is the difference in lattice constants between the substrate and the epitaxial layer) are less...
Material Parameters of InGaAsP Quaternary Alloy Grown on InP
This is a continuation from the previous tutorial - lattice-mismatch effects on semiconductor epitaxial growth. This tutorial describes the numerical values of various material parameters of InGaAsP quaternary alloy grown lattice-matched on InP. A knowledge of the band-structure parameters, such as the band gap and the effective masses of the conduction and valence bands, is necessary to calculate the radiative and nonradiative Auger recombination rates. The low-field minority carrier mobilities are also useful for calculating the diffusion coefficient that plays an important role in device performance. Tables 4-1 to 4-3 list the band gap, the lattice constant, the effective...
Lattice-Mismatch Effects on Semiconductor Epitaxial Growth
This is a continuation from the previous tutorial - what is molecular-beam epitaxy (MBE)? A defect-free epitaxial growth of one crystal lattice over another takes place if the lattice constants of the two materials are nearly identical. In the presence of a small lattice mismatch (less than 0.1%), growth occurs with an approximate match of the lattice sites in the interface region of two lattices. This approximate match is possible if there is an elastic strain at the interface, that is, each atom is slightly displaced from its original position at the boundary layer. Although a small amount of...
What is Molecular-Beam Epitaxy (MBE)?
This is a continuation from the previous tutorial - what are vapor-phase epitaxy (VPE) and metal-organic vapor-phase epitaxy (MOVPE)? In the molecular-beam epitaxial (MBE) technique, epitaxial layers are grown by impinging atomic or molecular beams on a heated substrate kept in an ultrahigh vacuum. The constituents of the beam "stick" to the substrate, resulting in a lattice-matched layer. The beam intensities can be separately controlled to take into consideration the difference in sticking coefficients of the various constituents of the epitaxial layers. The widespread use of MBE for the growth of different III-V semiconductors resulted from the original work...