R. D. Dupuis

Room‐temperature continuous operation of photopumped MO‐CVD AlxGa1−xAs‐GaAs‐AlxGa1−xAs quantum‐well lasers

Room‐temperature continuous operation (cw, 300 °K) of photopumped AlxGa1−xAs‐GaAs‐AlxGa1−xAs quantum‐well heterostructure lasers embedded in Cu under diamond windows is demonstrated. The quantum‐well heterostructures are grown by metalorganic chemical vapor deposition (MO‐CVD) and possess undoped (nd−na≲1015/cm3) or compensated (nZn∼1019/cm3, nSe∼8×1018/cm3) GaAs active layers of thickness Lz∼200 A.

Low‐threshold continuous laser operation (300–337 °K) of multilayer MO‐CVD AlxGa1−xAs‐GaAs quantum‐well heterostructures

Data are presented on multilayer AlxGa1−xAs‐GaAs quantum‐well heterostructures showing that cw 300–337 °K laser operation is possible at photoexcitation threshold levels (≲1.2×103 W/cm2, Jth≲500 A/cm2) comparable to better LPE double heterojunctions and much lower than all previous single or multiple quantum‐well heterostructures. These quantum‐well heterostructures are grown by metalorganic chemical vapor deposition (MO‐CVD) and consist of four 80–90‐A GaAs active layers coupled by three 80–90‐A AlxGa1−xAs (x∼0.35) barriers, all of which are sandwiched between 1‐ and 0.3‐μm AlxGa1−xAs (x∼0.40) confining layers.

Crystal synthesis, electrical properties, and spontaneous and stimulated photoluminescence of In1−xGaxP:N grown from solution

The growth of In1−xGaxP from solution at constant temperature is described, and the distribution coefficient and incorporation of Ga in the crystal and also donor impurities are discussed. The variation of the measured mobility with composition indicates that the direct‐indirect transition is near x=0.74. Photoluminescence data on direct and indirect In1−xGaxP:N are presented, and the energies of the band gap, nitrogen A line, and NN‐pair peaks are plotted as a function of crystal composition. The nitrogen A line (EN) is degenerate with the Γ conduction‐band minimum (EΓ) at a crystal composition of x ∼0.71. For x≤0.71 a resonant N‐trap state exists above the fundamental conduction band edge. The resonant N‐trap transition can be photoexcited into laser operation in x=0.69 In1−xGaxP:N at very high energy (2.246 eV–5520 A, 77 °K) where, in fact, the recombination transition is enhanced (EN∼EΓ).

Spontaneous and stimulated photoluminescence on nitrogen A‐line and NN‐pair line transitions in GaAs1−x Px : N

In accord with recent absorption measurements, photoluminescence measurements on crystals grown from a Ga solution, as well as on some vapor epitaxial crystals, indicate that the A line in GaAs1−x Px : N is higher in energy than formerly believed. Also, the NN‐pair emission peak (ENN) has been determined more accurately relative to the A‐line peak (EN), and relative to EΓ and Ex. For crystal composition x less than 0.9, only a single NN‐pair emission band is observed with ENN = EΓ at x ≈ 0.30. The A‐line is broad (⩾ 50 A) with EN = EΓ at x ≈ 0.40. For EN ≈ EΓ or ENN ≈ EΓ the recombination probability on transitions involving N traps may be resonantly enhanced. If EΓ is close to or degenerate with EN or ENN, carrier reemission from N traps to the conduction band is fast, and stimulated emission involving N or NN trap centers can lead to line narrowing because the excess electron population can readjust rapidly between trap centers and the Γ conduction band.

In1−xGaxP p‐n Junction Lasers

The laser operation of In1−xGaxP (x∼0.27) p‐n junctions is demonstrated at 4.2 and 77°K. The n‐type material for the junctions is grown at a fixed temperature (900–950°C) from an In solution with the InP and GaP source crystal introduced into the solution at slightly higher temperature. The p‐n junctions are formed at 700°C by Zn diffusion from an In + 10% Zn source. In comparison with InP, the threshold currents for In1−xGaxP junctions are large, which is attributed to the problems associated with introducing Zn into the In–Ga sublattice.

Crystal and luminescence properties of constant‐temperature liquid‐phase‐expitaxial In1−xGaxP (x [inverted lazy s]0.7) grown on (100) GaAs1−xPx (x [inverted lazy s]0.4)

The growth of In1−xGaxP (x [inverted lazy s]0.7) by liquid‐phase epitaxy at constant temperature (CT‐LPE) on [100]‐oriented GaAs1−xPx (x [inverted lazy s]0.4) is described. Spontaneous and stimulated photoluminescence (77°K) of n‐ and p‐type In1−xGaxP crystals is examined. For n‐type crystals, laser modes appear only on the lower‐energy side of the emission peak, whereas in p‐type crystals, laser modes are observed also on the higher‐energy side of the emission peak because of the high density of empty acceptor states ([inverted lazy s]5×1018/cm3) above the hole quasi‐Fermi level. The decreased absorption near the laser wavelengths of p‐type samples yields a value of [inverted lazy s]6.2 for the index expression (n‐λdn/dλ) in contrast to a value of [sine wave]7.0 for n‐type samples. p‐n junctions fabricated by Zn diffusion into the In1−xGaxP epitaxial layers exhibit spectral behavior similar to the photoluminescence spectra of p‐type crystals.

Photopumped laser operation of MO‐CVD AlxGa1−xAs near a GaAs quantum well (λ≳6200 Å, 77 °K)

Data are presented showing that AlxGa1−xAs (x∼0.42) grown by metalorganic chemical vapor deposition (MO‐CVD) will operate as a photopumped laser to wavelengths as short as ∼6200 A (77 °K). From the different spectral behavior of two separately photopumped epitaxial AlxGa1−xAs (x∼0.36) confining layers (1 and 0.3 μm thick) with an 80‐A (and a comparison 200‐A) GaAs quantum‐well center layer, the recombination of hot electrons with holes collected in the quantum layer is used to estimate ΔEv.

Optically Pumped In1−xGax P Platelet Lasers from the Infrared to the Yellow (8900−5800 Å, 77°K)

The laser operation (77°K) of optically pumped thin platelets of In1−xGaxP over the composition range x=0–0.59 (8900−5800°A) is demonstrated. The samples are prepared from material grown at constant temperature (900–1000°C) from In solution with source InP and GaP introduced at slightly higher temperature. The dependence of the laser photon energy upon composition agrees well with the Γ−χ curves of Lorenz and Onton and confirms the belief that the direct‐indirect transition is at x∼0.74. In addition, unique spectral data on In1−x Gax P (x=0.27) are presented that show the mode development from spontaneous to high‐level stimulated emission.

In1−x Gax P:N Laser Operation (cw, 77°K) on the Nitrogen A‐Line Transition in Indirect Crystals (x ≥ 0.74) and in Direct Crystals above the Fundamental Band Edge (x ≥ 0.71)

The laser operation (cw, 77°K) of In1−xGaxP on the nitrogen A‐line transition in indirect crystals (x≥0.74) and in direct crystals above the fundamental band edge (x≤0.71) is reported (5450 and 5470 A, respectively). Thin (1–5 μ) experimental samples are prepared from crystals grown from In solution by a modified Bridgman method. The crystals are doped with GaN or N from the quartz of the synthesis ampoule. The samples are mounted in a sandwich configuration with indium wetted onto a copper heat sink on one side and thin CdS (10–20 μ) and sapphire on the other side. The thin samples are volume excited in a tiny spot by an argon‐ion laser focused through the sapphire window and the CdS spacer which, with the sample, forms a high‐Q compound cavity.

Optically Pumped Volume‐Excited cw Room‐Temperature In1−x Gax P (x ≤ 0.60) Platelet Lasers

Room‐temperature cw laser operation well into the visible spectrum (λ ∼ 6000 A) is reported for In1−xGaxP (x ≤ 0.60). Thin (1–5‐μ) experimental samples are compressed into In, under a thick (∼ 250‐μ) high‐index (η > 2. 6) SiC window, with a thin (10–50‐μ) narrow SiC platelet under part of the In1−xGaxP sample. The thin In1−xGaxP samples, in the compound cavity, are volume excited in a small spot with an argon laser so that the heat is easily removed by the SiC windows and nearby In heat sink.