V. P. Germogenov

Manganese doping of In1−xGaxAsyP1-y films in liquid-phase epitaxy

The manganese doping of In1−xGaxAsyP1-y(0 ≦ y ≦ 1) films grown by liquid-phase epitaxy has been investigated. A study has been made of the influence of the solid-solution composition and of the method of introducing the manganese into the solution melt on the electrical properties of the films, and also on the surface morphology, the optical absorption edge, and the mismatch of the film and substrate lattice constants. It is shown that the hole density in the films decreases with decreasing y. The reasons for this are the decrease in the distribution coefficient of the acceptor manganese (from 0.3 to 0.001), the increase in the degree of compensation of the acceptors with donors (from 0.2 to 0.9), and the increase in the acceptor ionization energy. The composition of the InGaAsP:Mn film and the morphology of its surface depend on the method of preparation of the melt, this being explained by the strong interaction of the manganese atoms with the other components of the liquid phase.

Analysis of critical melt supercooling for heteroepitaxy of AlxGa1−xSb by GaSb

Thermodynamic computations of the critical supercooling of a melt are performed for the case of heteroepitaxy of a solid AlxGa1−xSb solution on a GaSb substrate for which there should be no substrate etching. Three kinds of supercoolings are examined, where Δcr(1) is the supercooling for which the change in the system Gibbs energy should equal zero because of dissolution, Δcr(1) is the supercooling for which the diminution in the system Gibbs energy due to substrate dissolution equals the energy being liberated during crystallization of the AlxGa1−xSb solid solutions layer. Finally, the influence of the specific free interphasal energy of the substrate-melt interface on the result of computing the critical supercooling (the supercooling Δcr(1) is considered.

Study of perfection of layers of AlGaSb(AS) solid solution

Studies have been carried out on the perfection of then-AlxGa1−xSb1−yAsy (0.12⩽x⩽0.26) layer grown on GaSb substrates under different conditions of lattice matching. During the relaxation of the mechanical stresses at first a system of tilt dislocations with a density of up to 5 · 105 cm−2 is formed while in thick layers (h ∼ 20 μm) a network of misfit dislocations parallel to the heteroboundary is formed. The time required to dissolve a weighed amount of GaAs in the melt is shown to be of major importance for obtaining layers of a solid solution that are isoperiodic with the substrate. The entry of arsenic only in the initial portion of the epitaxial layer can reduce the dislocation density in the layer without decreasing the measured value of Aa. Dissolution of a weighed amount of GaAs in a Ga + Sb melt for two hours at T=730–750°C is sufficient to obtain layers of AlxGa1−xSb1−yAsy solid solution that are isoperiodic with the substrate.

Formation of p-n junctions in tellurium-doped AlxGa1−xSb(As) (x = 0.15–0.20) solid solution layers

We study the variation of electron density n in depth of tellurium-doped epitaxial AlxGa1−xSb(As) (x = 0.15–0.20) layers. It is established that n decreases in proportion to the growth of the layer and, under definite conditions, the formation of p-n junctions in layers grown from a single melt or the growth of layers having an electron density below 1016 cm−3 is possible. It is shown that the cause of such a decrease of electron density is the variation of the composition of the solid solution in depth of the layer and the accompanying increase in the concentration of residual acceptor defects in the material.

Doping of solid solutions in liquid epitaxy. III. Tellurium in AlxGa1−xSb

A calculation is made of the dependences of the coefficient of the tellurium distribution KTe and the electron concentration n in AlxGa1−xSb on the composition of the solid solution and the growth temperature. It is shown that KTe must decrease with increasing x. The dependence of KTe on the temperature is also determined by x. Experimental results were obtained on AlxGa1−x Sb (0 ⩽ x ⩽ 0.74) films grown by liquid epitaxy. The electron concentration in the films was measured through the thermoelectric power and the capacitance-voltage characteristics of Schottky barriers. Satisfactory agreement with the results of the calculation was obtained.

Surface-barrier structures on AlxGa1−xSb. II. Band gap dependence of barrier height

The short-circuit photocurrent is used to find the forbidden gap width Eg and barrier height ΦB of Pd-n-AlxGa1−xSb (0.1 ⩽s x ⩽ 0.7) surface-barrier structure fabricated electrochemically. The barrier height was also determined from the capacitive voltage cutoff and the current-voltage characteristics. For metal-n-AlxGa1−xSb contacts the linear approximation to ΦB(Eg) is given by ΦB = 0.64Eg + 0.16 eV. In some samples the photoresponse spectrum has a hump, indicating the effects of deep levels.

Surface-barrier structures on AlxGa1−xSb. I. Preparation and physical model of the contact

The optimal conditions for preparing the surface and electrochemically depositing the metal have been determined for surface-barrier junctions of palladium on n-type gallium aluminum antimonide. The temperature and composition dependences of the voltage-current and voltage-capacitance characteristics of the junctions have been measured. When combined with the frequency dependence of the capacitance, these data show that, depending on the condition during formation, nearly ideal Schottky barriers are formed (i.e., a metal-intermediate layer-semiconductor system). The mechanism for current flow depends on the structure of the contact and the solid-solution composition. Anomalous barrier behavior at low temperatures is due to specific properties of the solid solution.

Alloying of solid solutions during liquid-phase epitaxy: II. Gallium aluminum antimonide

This paper considers the process of alloying during the liquid-phase epitaxy of an ideal solution of the type AxIII B1−xIII Cv with groups II and IV admixtures. Analytic expressions are obtained for the acceptor and donor distribution coefficients as functions of the composition of the solid solution. It is shown that in the case of group II acceptors, the distribution coefficients should decrease as the forbidden bandwidth of the solid solution increases. The x dependence of group IV acceptors and donors may be more involved.

Cathodoluminescence from epitaxial layers of p-Alx Ga1−xSb

The cathodoluminescence (CL) of doped and undoped layers of p-AlxGa1−xsb(0≤x≤0.8) grown by liquid-phase epitaxy has been investigated. Changing the composition of the solid solution resulted in emission bands having maxima between 0.77 and 1.58 eV at 77°K and between 0.72 and 1.55 eV at 300°K. It is shown that the following factors play a role in determining the luminescence intensity as a function of x: 1) the transfer of electrons to the L minimum in the conduction band; 2) a decrease in the hole concentration in the layers; 3) a decrease in the concentration of nonradiative recombination centers. The CL spectrum at 77°K contains a longwavelength band whose behavior is attributed to recombination through a level similar to the level known to be present in GaSb and believed to be caused by an intrinsic defect. The ionization energy of this level increases as x increases.

Appearance of flaws in layers of AlxGa1−xSb solid solutions during epitaxial growth from the liquid phase

Layers of AlxGa1−xSb (x≤0.7) solid solutions were grown epitaxially from the liquid phase on substrates of gallium antimonide. Aluminum was added to the melt during the buildup of an epitaxial layer. In these layers were found inclusions of the solvent as well as regions of localized chemical inhomogeneities. It is shown here that the appearance of such flaws is intimately related to the relief which the GaSb substrate has formed by the time aluminum enters into the solution. A mechanism of this flaw formation is suggested.